How effective is laser treatment for acne

The advancement in science brings with it new modalities of treatment for medicine. One of it is laser technology. It has found application in various fields of medicine, such as surgery and dermatology. Laser is being used extensively in various surgical operations, liposuction, varicose veins ablation and aesthetic treatments.

Light therapy is the latest addition in the arsenal of treatment for acne. Laser, which produces a high-energy beam of light of precise wavelength, is the most common light source in acne therapy. It selectively damages Propionibacterium acnes, the bacteria responsible in the formation of acne.  It acts on the porphyrins, the pigment being produced by the said bacteria, which in turn causes sensitization and its subsequent destruction.  

The popularity of laser and other light-sources is prompting several studies regarding its application in acne treatment.  Under investigation are broad-spectrum continuous wave visible-light sources (blue light and blue-red light), specific narrow-band light, intense pulsed light (IPL), pulsed dye lasers (PDL), potassium titanyl phosphate lasers, infrared diode lasers and photodynamic therapy (PDT) with or without photosensitizing agents (aminolevulinic acid or methyl-aminolevullinic acid).

To date substantial evidence in support of light therapy as mode of treatment in acne is lacking. Outcomes of some trials are contradictory. In a study by Haedersdal , red-light-activated methyl-aminolevulinic acid-PDT and aminolevulinic acid-PDT were efficacious in 50-60% of patients up to 20 weeks after one to three weeks of treatment. In another study by Wiegell et al, effect lasted up to 1 year after treatment.  Moreover, IPL-assisted PDT seems to be more effective than IPL alone.

Some studies compared the efficacy of broad-spectrum light sources versus existing topical treatments. Blue light twice-weekly for 4 weeks was reported to be superior to topical clindamycin. Mixed blue-red light daily for 12 weeks reduced more acne lesions than BPO.

Kumaresan and Snirivas evaluated the efficacy of single against burst-pulse mode in IPL therapy. They have concluded that IPL as single therapy was beneficial in the treatment of acne. Results also showed that burst-pulse mode was better than the single pulse mode in clearing acne.

Despite the studies, laser treatment is not considered the first choice in the treatment of acne today. It only serves as an adjunct to medical therapy.  Significant improvement is observed when laser is utilized in combination with topical and systemic medications.

References:

1. Treating acne vulgaris: systemic, local and combination therapy: Adjunctive therapies. Medscape
2. Kumaresan M, Srinivas CR. Efficacy of IPL in treatment of acne vulgaris : Comparison of single- and burst-pulse mode in IPL. Indian J Dermatol [serial online] 2010 [cited 2011 Feb 27];55:370-2. 

Related Articles:

1. Can chocolates cause acne flare-ups
2. Hormonal treatment for acne
3. What are adjunctive therapies for acne
4. Why should pimples be a cause for concern

Can chocolates cause acne flare-ups?

Ghirardelli chocolate

Have you ever noted pimple breakouts after indulging on your favorite brown sweets? Or have you ever associated zit eruptions with chocolates? Well, there may be truth in your observation after all.

Earlier studies revealed no direct connection between chocolate consumption and acne breakouts. Tests that were conducted before to suggest the association of diet and acne have used chocolate candies, containing added ingredients such as milk, sugar and nuts. So far only milk was proven to have a direct link to acne exacerbation.

However, at the recently concluded 69^th Annual Meeting of the American Academy of Dermatology a report was presented associating acne with consumption of pure chocolate.

In a study conducted at the University of Miami Miller school of Medicine in Florida, researchers have involved 10 healthy male subjects between 18 to 35 years of age with a history of facial acne vulgaris, who had at least I, but no more than 4 acneiform lesions (blackhead or whiteheads, papule and cyst). They were instructed to consume 6 ounces of 100% Ghirardelli chocolate daily for duration of 1 week.

A significant increase in the number of lesions was found, suggesting a strong correlation between the amount of chocolate that was consumed and the amount of acneiform lesions developed.

Further studies though are needed to establish the relationship between chocolate and acne and the mechanism that is involved in it.

Source:

Chocolate May Exacerbate Acne in Men. Medscape Medical News. 

Hormonal Treatment for Acne

oral contraceptive pills

I have mentioned in my earlier post “Why should acne be a cause for concern” that hormones play a role in the pathogenesis of acne. Even before the onset of puberty adrenal glands are already producing larger amounts of dehydroepiandrosterone sulfate (DHEAS), which can be metabolized into more potent androgens, leading to cascade of events that trigger acne formation. In women, excess production of androgens by the ovary as a result of Polycystic Ovary Syndrome may also cause acne. These are the reasons behind the use of hormones in the treatment of acne.


Hormonal therapy is most effective in adult females with persistent facial inflammatory papules and nodules. We may have heard of women complaining of acne flare before or during menstruation. Therefore, hormone intervention is an additional option in the therapeutic arsenal for female patients with acne. 


When should hormonal therapy be initiated in acne cases?

• when acne has not responded to standard treatment (topical and oral antibiotics or its combination)
• when there are contraindications to intake of isotretinoin
• when rapid relapse has occurred after repeated courses of isotretinoin
• when menstrual control and/or contraception are required alongside acne therapy

Nevertheless, it is also noteworthy that this kind of treatment can also be very effective in females with acne whether their serum androgens are normal or abnormal. Females with acne have higher levels of serum androgens compared with women without acne, though these levels are mostly within the normal range.

I.           Inhibitors of Adrenal Androgen Production

Glucocorticoids in low doses can suppress the adrenal production of androgens. They are indicated for patients, both male and female, who have an elevated DHEAS level associated with late-onset congenital adrenal hyperplasia, caused by an inherent deficiency of 11-hydroxylase or 21-hydroxylase enzymes. Low-dose prednisolone (2.5–5 mg) or dexamethasone (0.25–0.75 mg) given at night (or alternative nights) can be sufficient to suppress adrenal androgen production and subsequently reduce sebum (oil)production by up to 50% with a concomitant improvement in acne.

Several studies have shown that glucocortioids given alongside cyclical estrogen (i.e., oral contraceptives) can successfully reduce sebum production in recalcitrant acne via reduction in plasma androgen level than with either agent alone.

II.        Inhibitors of Ovarian Androgen Production

1.   Estrogen

Estrogens are particularly valuable in women with clinical evidence of hyperandrogenism ( e.g., hirsutism or excessive hair growth,  menstrual irregularity, acne and oily skin). It shows two-pronged action. First, estrogen increases the hepatic production sex hormone-binding globulin, which binds and thus reduces levels of free circulating testosterone. Second, estrogens suppress the ovarian production of androgens by suppressing gonadotrophin release from the pituitary, resulting in lower serum androgen levels, hence less seborrhea.

The ones recommended for the treatment of acne are usually oral contraceptives with combined preparation containing estrogen (most commonly ethinyl estradiol) and a progestin with anti-androgenic activity.

Oral contraceptive pills containing ethinylestrodiol (oestrogen) and an antiandrogenic progesterone  include cyproterone acetate (co-cyprindiol or Diane™-35, Estelle™ 35, Ginet-84™and Althea), drospirenone (Yasmin™, Yaz™) or dienogest (Valette™).

Combined oral contraceptives can increase the risk of thromboembolism (blood clots blocking blood vessels), especially in those with an inherited tendency ("thrombophilia"), or who smoke.  Minor side effects are breast tenderness (20%) and increase in bra size, Spotting" (irregular mild bleeding between periods) occurs in 10% of women in the first month, nausea and loss of appetite, headaches, increased appetite and weight increase (uncommon), mood changes including depression, melasma (facial pigmentation) and hair loss.

2.   Gonadotrophin-releasing Agonists

Gonadotrophin releasing agonists inhibit ovarian androgen production by interrupting the cyclical release of luteinizing hormone and follicle-stimulating hormone from the pituitary.  Nafarelin, leuprolide and buserelin are included in this group. They all have demonstrated efficacy in the treatment of acne and hirsutism in females both with and without endocrine abnormalities. . However, their use is limited somewhat by the potential for adverse effects including reduced bone mass, headache and menopausal symptoms, caused by the suppression of ovarian estrogen production.

 

III.     Androgen Receptor Blockers

1.   Cyproterone Acetate

Cyproterone acetate  (CPA) is a progestional anti-androgen that directly inhibits the androgen receptor. It  reduces sebum production by no more than 30%, but its success in acne is enhanced by its direct effects on androgen-mediated comedogenesis (i.e. blackhead and whitehead formation). . An overall improvement in acne has been reported in up to 90% of patients treated with higher doses of CPA (50–100 mg/day), with or without ethinyl estradiol.

Is it okay for men suffering from acne to take CPA? It has been demonstrated that 25mg of CPA can  improve acne in males. However, due to its feminization effects, such as reduced libido, gynecomastia (breast enlargemement) and azoospermia (absence of sperm in the ejaculate) this kind of treatment is not recommended for males. General side effects of CPA, although uncommon, include fatigue, headache, nausea, weight fluctuation, liver dysfunction and blood clotting abnormalities.

2.   Spironalactone

Spironolactone is a potassium-sparing medication used as a diuretic medication for heart failure, liver disease and high blood pressure. However, it has also been found useful for hirsutism, acne and seborrhoea because it has anti-androgenic properties. Spironolactone works by blocking androgen receptors.

                It can reduce sebum production by 30–75% depending on the dose. It is usually prescribed at a dose of 50–100 mg daily with meals, but many women with sporadic outbreaks can be successfully managed with as little as 25 mg daily. As with other hormonal therapies, response is slow and it may take up to 3 months of continuous treatment before any benefit is observed.

Menstrual irregularities, potential hyperkalemia, breast tenderness, fatigue, headache, fluid retention and, rarely, melasma are among the side effects.  Spironalactone should not be prescribed for male patients because like CPA it can also cause feminization. Females should be advised to avoid pregnancy owing to potential abnormalities to the male fetus. All patients should undergo regular monitoring of their electrolytes owing to the potassium-retaining effects of spironolactone on the kidney.

3.   Flutamide

Flutamide is a nonsteroidal potent androgen antagonist, most routinely used in the treatment of prostate cancer. It has been demonstrated to be efficacious in treating androgen-mediated acne and hirsutism when administered at a dose of 125–250 mg daily.

Like all hormonal agents, it should not be prescribed for male patients and owing to the risks of teratogenicity, pregnancy should be avoided.

Fatal hepatotoxicity has been reported with flutamide,  that is why many countries now ban the use of flutamide as a treatment for androgen-mediated acne and hirsutism.

Other skin/hair conditions, aside from acne aggravated by androgenic hormones and therefore hormonal therapy is applicable are:

• Seborrhoea
• Hirsutism
• Female pattern hair loss
• Hidradenitis suppurativa

Hormonal therapy carries multiple side effect, thus it requires monitoring. Patients therefore are advised not to self-medicate. Always seek advice from your dermatologist or gynecologist regarding the appropriate medicine for your condition.

References:

1. Treating Acne Vulgaris:Systemic, Local and Combination Therapy. Medscape
2. Hormonal treatment . DermNet NZ

Related articles:

1. What is Hormonal Imbalance?
2. Why should pimples be a cause for concern?

What are adjunctive therapies for acne?

A number of physical therapies are available for treating active acne.  These procedures aid in faster resolution of active lesions in acne, but should not be utilized as a first-line of treatment. They are recommended to be used in conjunction with medical therapy to prevent the development of new lesions.

These are office procedures that require skill, hence should be performed only by dermatologists and trained aesthetisticians.

1.      Acne surgery 

Using a comedone extractor, it facilitates immediate expulsion of comedones and drainage of pus in cystic lesions.

removal of comedones

2.      Hyperfrecation

Macrocomedones are usually closed comedones (whiteheads) but are occasionally open comedones (blackheads) up to 1.5 mm in diameter. Light cautery or hyfrecation after the application of local anesthetic cream (e.g., EMLA) has been demonstrated to be successful in the treatment of multiple macrocomedones. The topical anesthetic is applied for 60–90 min beneath an occlusive adhesive dressing, after which cautery is used to provide very low-grade thermal damage in order to stimulate the body's own defense mechanisms to induce resolution of the comedo. This takes seconds to perform and should be painless. There is very little associated scarring or postinflammatory hyperpigmentation and it is generally well tolerated.

3.      Chemical Peels

Glycolic acid and salicylic acid peels are also beneficial in mild-to-moderate comedonal acne in women aged 13–40 years. They promote desquamation, which reduces corneocyte adhesion and follicular plugging, enabling the extrusion of inflammatory contents.

application of glycolic acid

4.     Intralesional  Steroid Injections

Larger inflammatory nodules and cysts respond well to intralesional injections with triamcinolone acetonide, with a rapid reduction in pain and swelling. A 30-gauge needle is used to inject 1–2 mg/ml triamcinolone acetonide into the center of the lesion until the erythema blanches. Injections can be repeated if necessary every 3 weeks. 

injection directly into the lesion

5.      Cryotherapy

If large inflammatory lesions persist beyond 2 weeks, cryotherapy is the preferred option. Superficial freezing with liquid nitrogen will hasten the resolution of such lesions and is relatively painless. Two 15–30-s freeze–thaw cycles are recommended.

6.      Light therapy

Lasers are the most common light sources utilized in acne therapy, which produce a high-energy beam of light of a precise wavelength range. A range of treatments are currently being used, including broad-spectrum continuous wave visible light sources (blue light and blue–red light), specific narrow-band light, intense pulsed light (IPL), pulsed dye lasers (PDL), potassium titanyl phosphate lasers, infrared diode lasers and photodynamic therapy (PDT) with or without photosensitizing agents (aminolevulinic acid or methyl-aminolevulinic acid). Light therapy exerts a selective cytotoxic effect on the proprionibacteria, which appear to be more susceptible to short-term damage from light therapies than keratinocytes. Comedonal and proinflammatory cytokines are also suppressed.

Why should pimples be a cause for concern?

When I was about 10 years of age my skin began to change. I started having bumps on my face. I begged my father to bring me to a doctor. But people back then didn’t believe that pimples need to be treated. They adhere to the belief that it would disappear on its own upon reaching adulthood. Until now some people still think that way about pimples or acne. But why do we need to seek medical care for it?

First of all, acne is a cause of embarrassment for most teenagers and even adults. Their once smooth skin becomes rough and bumpy. They could not even look straight into other people’s faces anymore.  They were afraid of being stared at or laughed at. These people experience impaired self esteem, anxiety and clinical depression as a direct consequence of acne, which can lead to social isolation, interpersonal difficulties and even suicidal ideation. In a study of 60 adult patients with acne, Lasek et al. found that patients reported emotional effects as a consequence of their skin condition that were similar in magnitude to those reported by patients with psoriasis, which is traditionally regarded as a condition causing significant psychological disability. According to the results of a retrospective Swedish cohort study it was observed that the risk for attempted suicide was increased in patients with severe acne 6 months before and after treatment.  Even mild/moderate acne can be associated with significant depression and suicidal ideation.

Secondly, acne can leave scars which are permanent. It would be there for life even after the pimples are long gone. Patients who scar have an even higher prevalence of psychological morbidity when compared with non-scarring acne sufferers. Scars are difficult to remove even with the advent of dermabrasion and laser resurfacing.

What is Acne Vulgaris?

Acne vulgaris refers to the inflammation of a pilosebaceous unit in areas rich in sebaceous or oil glands, such as the face, neck, chest or back. It is the medical term for pimples. Most people call the huge zits on the face acne. It is a common misconception. Acne is characterized by a combination of lesions, such as blackheads (open comedones) and whiteheads (closed comedones), inflammatory papules and pustules and the nodulocystic lesions. Severe cystic acne affecting other areas aside from the face is called acne conglobata.

open comedones

Acne occurs at the onset of puberty due to the complex interaction of gonadotrophic hormones and bacteria (Propionibacterium acnes) in genetically predisposed individuals. Androgens stimulate increased sebum production by sebaceous glands. On the other hand, bacteria secrete lipase which converts lipids to fatty acids. The combination of sebum and fatty acids causes a sterile inflammatory reaction in the pilosebaceous unit with resultant hyperkeratinization of the lining of the follicle and its subsequent plugging. This is how comedones are being formed.  When comedones rupture into the dermis it resembles a foreign body, giving rise to an inflammatory response with pustule and abscess formation. Destruction of the surrounding tissue leads to scar formation. multiple erythematous papules and comedone

The tendency to develop acne runs in families. It can be triggered by certain factors such as exposure to acnegenic mineral oils, intake of drugs (lithium, hydantoin, topical and systemic corticosteroids  and oral contraceptives),  endocrine factors (polycystic ovary syndrome), emotional stress, lack of sleep, occlusion and pressure on the skin by leaning face on hands or telephones and improper care of the skin.

Can some food aggravate acne condition?

Population-based and migration studies have suggested a correlation between diet and acne. Large, well-controlled, observational studies have demonstrated that diets high in dairy products are associated with an increase in the risk for and severity of acne. The relationship between milk and acne severity may be explained by the presence in dairy of normal reproductive steroid hormones or the enhanced production of polypeptide hormones such as IGF-1, which can increase androgen exposure, and thus, acne risk. Recent findings also describe an association between a high-glycemic-index (i.e., carbohydrates that break down quickly during digestion and release glucose rapidly into the bloodstream) diet and longer acne duration. No study has established a positive association between acne and chocolate, saturated fat, or salt intake.

Treatment measures to be carried out by the patient

• .     Wash your face with soap twice a day. Do not scrub too roughly.
•      Do not use greasy cream on the face.
•      Avoid pancake-type makeup which may contain oil, grease or wax.
•     Boys should not use oils, greases, pomades or hair tonics. Shave regularly.
•     Have at least 8 hours of sleep each night.
•     When getting out in the sun do not use oily or greasy suntan preparations.
•      Don’t prick pimples on your own as this may lead to scarring.

Medical treatment for acne

The choice of acne therapy is largely determined by the severity and extent of the disease, but should be influenced by a number of other factors including disease duration, response to previous treatments, predisposition to scarring and post-inflammatory hyperpigmentation, as well as patient preference and economics. Patients with mild acne usually require topical treatment alone. Those with more extensive acne should be prescribed topical agents in conjunction with appropriate oral therapy. 
Many topical preparations for acne are available. These are:

•  topical retinoids
•  benzoyl peroxide
•  azelaic acid 
•  topical antibiotics

Most of the time a combination of these agents is necessary for a successful outcome. Antibiotics and/or hormonal treatments are employed for more severe or treatment-resistant disease. Systemic retinoids provide extremely efficacious therapy for severe disease that has not responded to combination therapy.

Your dermatologist should guide you on the step-by-step approach to treatment of acne. Bear in mind that resolution of pimples doesn't happen overnight. Response to treatment might be slow and there could even be a flare-up of acne on the onset of treatment. Any local preparation that was prescribed should be continued for months or even  years if you continue to have complexion problems.

You may experience occasional flare-ups and when this happens it is imperative that you begin active medical therapy with your dermatologist to avoid scarring of the skin.

References:

1. Diet and Acne, A Myth? Medscape
2. Severe Acne Linked to Suicide Risk Even Before Treatment Is Started. Medscape 
3. Acne Conglobata. Emedicine. Medscape
4. Treating Acne Vulgaris,:Systemic, Local and Combination Therapy. Medscape
5. Does Diet Really Affect Acne? Medscape

Secrets of a healthy and young-looking skin

We all want to stay young and beautiful forever. Who would like to look old and wrinkled? The answer is obvious. Throughout history people have always been in a quest to stay young. The first emperor of China Qin Shi Huang ingested mercury pills, believing it could lead him to immortality. Cleopatra kept an impeccable complexion by bathing in milk and honey. Famous celebrities then and now are seeking various ways, whether natural or otherwise to maintain their youthful look.

Are there really ways to slow down the aging process? What are the secrets to a healthy and glowing skin?

You need to start early to keep yourself feeling young and looking young. It cannot be done overnight. It needs to be done as early as in your 20s. Follow a healthy skin habits religiously. Moreover, adopt a holistic approach to achieve optimum result. Our skin is a reflection of our overall well-being.

Incorporate these healthy habits into your daily regimen. You won’t only have a beautiful skin, but also a healthy body.

1. Use a gentle  cleanser everyday

Use a natural, mild cleanser to wash your face and body. Synthetic detergents and hot water are harsh for the skin. Avoid commercial scrubs too.

2.  2.  Always moisturize after cleansing

It is recommended to apply a moisturizing cream to replenish the oil that was lost after bathing or cleansing.

3.  3. Use a night cream

Cleanse your face before going to bed. Remove all the make-up that you wore during the day. I advise applying a night cream that contains retinol which is proven to diminish fine lines.

4.  4. Protect your skin from the sun

Moderate sunlight promotes the synthesis of Vitamin D. But prolonged exposure is hazardous to your skin. It leads to premature skin ageing, loss of elasticity and skin cancer. Even indoor tanning is not good for the skin.

To protect your skin from the sun avoid going out between 10 Am to 4 PM. If you expect to be out for more than 20 minutes, wear a wide-brimmed hat, sunglasses and protective clothing or carry an umbrella. Whether it is summer or winter always apply sunscreen during the day even if you are staying indoors because a certain amount of UV radiation still penetrates our window glasses. For prolonged exposure wear a broad spectrum sunblock 30 0r 50+ for better protection.

5.  5. Beauty sleep

Sleep for at least 7 to 8 hours a t night to avoid having dark hollows under your eyes or eye bags. Chronic lack of sleep results to higher stress hormone level like cortisol, leading to premature aging. 

6. 6. Exercise regularly

Get a minimum of 30 minutes of exercise daily. Exercise increases sweating and cutaneous blood flow.

7.7. Stress management

Make time for relaxation. You may try activities such as yoga or meditation, even though others may find dancing and gym workout more stress-relieving.

8. 8. Don’t smoke

Smoking is devastating to health. Nicotine constricts blood, impairing blood flow to the skin. With less blood blow our skin doesn’t get as much oxygen and important nutrients, such as Vitamin A. Chemicals in tobacco smoke also damages our skin’s collagen and elastin, which are fibers that give your skin strength and elasticity. As a result, skin wrinkle and sag prematurely.

9.  9. Healthy diet

·        Water: For clear healthy skin, drink approximately 8 glasses of water a day to hydrate the skin. Even mild level of dehydration can make the skin dry.

·        Whole grains: Replace refined carbohydrates, such as pasta, bread and cookies with whole grains. Whole grains contain not only beneficial phytochemicals and anti--aging antioxidants, but Vitamin E, magnesium and fiber as well.

·         Fiber: Fiber is also important to maintaining healthy skin. As with water, eating fiber prevents constipation, which can be detrimental to skin health. To get more fiber, consider adding more fruits and vegetables in your diet.

·         Omega-3 fatty acids: Omega-3 fatty acids strengthen cell-membranes. Sources of omega-3 fatty acids are cold water fish, (e.g., salmon, herring, mackerel, tuna, sardines), krill, flaxseed, purslane, green-lipped mussel, eggs, milk and cheese and olive oil.

·        Vitamin-C rich food: Vitamin C is involve in the formation of collagen- a protein that binds call and tissues together. Vitamin C is also an antioxidant, which blocks some of the effects of free radicals, the one responsible for the aging process. Some excellent sources of vitamin C are oranges, green peppers, watermelon, papaya, grapefruit, cantaloupe, strawberries, kiwi, mango, broccoli, tomatoes, Brussels sprouts, cauliflower, cabbage, pomegranate and citrus juices or juices fortified with vitamin C.

·        Soy: Soy contains isoflavones that stimulates the development of skin cells. It also reduces the breakdown of collagen and prevents the fats in the skin from turning into aggressive compounds. The highest level of isoflavone can be found in whole bean products that have not been highly processed. Although many varieties of vegetables, grains, and legumes contain small amounts of isoflavones, by far the largest quantities are found in soybeans. Roasted soy nuts, tofu, tempeh, soy milk, meat substitutes, soy flour, and some soy protein isolates are also high in isoflavones. The soy germ, found in whole soybeans, is particularly high in isoflavones.

Always remember these basic tips and you won’t go wrong.  A healthy lifestyle leads to healthy skin.

Basic Facts about the Skin: Structure and Function

The skin is the body’s largest organ. It is the outer covering of the entire body and is continuous with the mucous membrane of the mouth, nose, urogenital organs and the anus. In an adult, the skin measures 1.5 to 2 sq.m., while the thickness varies from a fraction of a millimeter (eyelids, external acoustic meatus) to 4 mm. on the palms and soles.

The skin has a matt tinge due and peculiar color due to the color of its component tissues, the thickness of the granular and horny layers of the epidermis, the blood vessels visible through the skin, and the presence of the pigment melanin. The color of skin may change because the amount of pigment in it varies due to internal and external factors.

The skin performs various functions

• Protective barrier
•   Organ of sense
• Thermoregulatory function (regulates body temperature)
• Secretory and excretory function  (production of sweat and sebum and elimination of water, some chemicals and drugs through the skin)
• Respiratory function (absorption of oxygen and elimination of carbon dioxide
•  Metabolism of water, minerals, hormones and vitamins

The skin has three layers: the epidermis, dermis and subcutaneous tissue.

Epidermis

The epidermis is the most superficial of the layers of the skin. It is relatively thin, averaging in thickness to about less than 1 mm, yet tough. It is composed mainly of keratinocytes, which develop into 5 layers:

(1)  germinative layer (stratum basale)

(2)  prickle-cell layer (stratum spinosum)

(3)  granular layer (stratum granulosum)

(4)  stratum lucidum

(5)  horny layer (stratum corneum).

Stratum basale is the innermost and contains the youngest, differentiating cells, while stratum corneum is the outermost , made up of dead cells that are constantly shedding. The chemical protein in these cells is called keratin which is capable of absorbing vast amount of water. This is readily seen during bathing, when the skin of the palms and soles become white and wrinkled; albeit the cornified layer provides a major barrier of protection for the body by preventing bacteria, viruses and other foreign substances from entering the body. The epidermis (along with the other layers of the skin) protects the internal organs , muscles, nerves and blood vessels against trauma. In certain areas which require greater protection, such as the palms and soles, the horny layer of the epidermis is much thicker.

Melanocytes, which are the pigment-producing cells of the epidermis can be found in the basal layer.  Melanin’s primary role is to filter out ultraviolet radiation from the sun. That is why incidence of skin cancer is higher in Caucasians because the amount of pigment in their skin is low. It is interesting to note that the number of melanocytes in both dark and fair-skinned individuals is the same.  It is now accepted that the degree of skin pigmentation is determined by the functional capacity of the these cells and not by their amount.

The epidermis also contains Langerhan’s cells, which are part of the skin’s immune system. However, these cells are also responsible for the development of skin allergies.

Another group of cells that can be found in the epidermis and is primarily located in the basal layer are Merkel’s cells. They are assumed to function as touch receptors.

The epidermis is devoid of blood vessels.

Dermis

The dermis is located between the epidermis and the subcutaneous tissue. It consists of connective tissue, cellular elements and ground substance.It has a rich blood and nerve supply and contains sweat and oil glands and hair follicles.

Two layers are distinguished in the dermis: the papillary and reticular layer. The papillary layer are composed of thin bundles of collagen fibers, while in the reticular layer the collagen bundles are more compact and thick and intertwine into a thick network of loops.

Collagen, reticulin and elastic fibers comprise the connective tissue component of the dermis. They contribute to the flexibility and strength of the skin.

The cellular elements of the dermis include fibroblasts, endothelial cells, mast cells, histiocytes (macrophages), lymphocytes and plasma cells. Histiocytes play a predominant role in phagocytosis of bacteria and particulate matter in pathologic condtions and also of antigens in immune processes.

Lymphocytes and plasma cells are found only in a small number in normal skin, but their number significantly increase under pathologic conditions.

The ground substance of the dermis is a gel-like amorphous matrix, consisting of proteins, mucopolysaccharides, soluble collagens, enzyme, immune bodies, metabolites and many other substances.

The nerve endings sense pain, touch, pressure, and temperature. Some areas of the skin contain more nerve endings than others. For example, the fingertips and toes contain many nerves and are extremely sensitive to touch.

The sweat glands produce sweat in response to heat and stress. Sweat is composed of water, salt, and other chemicals. As sweat evaporates off the skin, it helps cool the body. Specialized sweat glands in the armpits and the genital region (apocrine sweat glands) secrete a thick, oily sweat that produces a characteristic body odor when the sweat is digested by the skin bacteria in those areas.  Eccrine sweat glands produce sweat which has a weak acid reaction. This helps to neutralize the damaging effect of chemical substances and prevents penetration of micro-organisms into the skin.

The sebaceous glands secrete sebum into hair follicles. Sebum is an oil, that keeps the skin moist and soft and acts as a barrier against foreign substances. The chemical compostion of the sebum contributes greatly to the bactericidal properties of the skin.

The hair follicles produce the various types of hair found throughout the body. Hair not only contributes to a person's appearance but has a number of important physical roles including regulating body temperature, providing protection from injury, and enhancing sensation. A portion of the follicle also contains stem cells capable of regrowing damaged epidermis.

The muscles connected to the hair follicles (mm. arrectores pilorum) and muscle fibers in the walls of blood vessels and sweat glands are the smooth voluntary muscles of the skin. When the arrectores pilorum muscle contracts, it raises the hair and squeezes out the secretion from the sebaceous glands. Smooth muscle fibers which are not connected to the hair follicles are present in the skin of the scalp, forehead, cheeks, and dorsal surfaces of the hands and feet.

The blood vessels of the dermis provide nutrients to the skin and help regulate body temperature. Heat makes the blood vessels enlarge (dilate), allowing large amounts of blood to circulate near the skin surface, where the heat can be released. Cold makes the blood vessels narrow (constrict), retaining the body's heat.

Over different parts of the body, the number of nerve endings, sweat glands and sebaceous glands, hair follicles, and blood vessels varies. The top of the head, for example, has many hair follicles, whereas the soles of the feet have none.

Subcutaneous layer

The subcutaneous layer serves as a receptacle for the formation and storage of fat. It supports the blood vessels and the nerves that pass from the dermis above to the tissue beneath. This layer constitutes the largest volume of adipose tissue in the body. The subcutaneous tissue protects the body from mechanical injuries and cooling

The thickness of the subcutaneous layer varies in different areas, as well as in different individuals. The amount of fatty tissue is practically nil on the eyelids, under the nails, on the prepuce and scrotum and there is very little of it on the nose, ears and vermillion border of the lips.

Notes:

1. Itching is a mild sensation of pain because of its lower-frequency of stimuli.
2. Shaving of excess hair does not promote more rapid growth of coarse hair. If allowed to grown normally, the hairs appear  and feel no different than before 
3. The value of intermittent massage on the scalp hair growth has not been proved.
4. Hair cannot turn gray overnight. The melanin pigmentation, which is distributed throughout the length of the hair shaft, takes weeks to be shed through the slow process of hair growth.
5. Heredity is the greatest factor predisposing to baldness, and an excess of male hormones may contribute to it.

 References: 

1.   Yu K. Skripkin and M.V. Milich, Skin and Venereal Diseases, pp.27-51 
2.    John C.Hall, MD, Sauer’s Manual of Skin Diseases, pp.1-5
3.      University of Maryland Medical Center http://www.ummm.edu/dermatology-info/directory.htm
4.    Merck Manual Home Edition http://merckmanuals.com/home/sec18/ch201b.html

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