Your skin is your largest organ. It covers your body tissues and internal organs and protects them from injury and infection. Skin is made up of two layers: a thin outer layer called the epidermis and a thicker inner layer called the dermis. Under the dermis is a layer of fat called subcutaneous tissue. The outer part of the epidermis is made up of dead cells and keratin (a tough, ﬁbrous type of pro- tein), which form a protective covering. These dead cells are constantly shed and then replaced by new cells. The inner part of the epidermis is made up of living cells that divide rapidly to produce those new cells. Certain cells in the epidermis produce the pigment known as melanin, which protects your skin and deter- mines your skin color.
The dermis is made up of connective tissue and contains structures such as hair follicles, sweat glands, sebaceous glands (which produce an oily substance called sebum), blood vessels, lymph vessels (which carry lymph into and out of the lymph glands), and nerves. Your skin also has some other important roles, including sensation—such as touch, temperature, and pain—and regulation of body temperature through perspiration and dilation (widening) and constriction (narrowing) of blood vessels.
Your hair is an extension of your skin. Hair is made up of dead cells and ker- atin. Each hair shaft has a spongy core (medulla), a surrounding layer of thin ﬁbers (cortex), and a thin covering of overlapping cells (cuticle). Each hair is rooted in a hair follicle (a tiny pit in the surface of the skin), from which it grows. While a hair is growing, the hair root is surrounded by live tissue called a bulb, which supplies keratin to the hair. Certain cells at the base of the hair follicle produce melanin, which determines your hair color. The main function of hair is protection.
Sunburn and Protecting Your Skin from the Sun
Too much exposure to ultraviolet rays from the sun, sunlamps, or tanning beds produces sunburn. The most common symptom of sunburn is red, swollen, and painful skin that can blister. If the sunburn is severe and covers a large portion of your body, you may also experience chills, fever, nausea, and vomiting. Repeated sun exposure also can produce harmful long-term effects, including wrinkling, premature aging of the skin, and skin cancer (see page 428). The most serious type of skin cancer, malignant melanoma (see page 428), is often fatal.
People who are most likely to be sunburned and who are most at risk for sun- induced skin cancer are those with fair skin, blue eyes, and red or blond hair, although anyone who spends time outdoors is at risk. The more sun exposure you receive, the more your skin is damaged. Certain medications—such as the antibiotic tetracycline, some diuretics (water pills), some tranquilizers, birth control pills, and over-the-counter antihistamines—make the skin more sensi- tive to the sun, increasing the likelihood of being sunburned. You are at risk for sunburn even on cloudy days; clouds do not block sunlight—they merely scatter the sun’s rays.
There are a number of simple steps you can take to protect yourself from the harmful rays of the sun. Try to plan outdoor activities for early in the morning or late in the afternoon so you can avoid being in the sun between 10:00 AM and
3:00 PM, when the sun’s rays are strongest. When you are out in the sun, use a sunscreen with a sun protection factor (SPF) of 15 or higher that protects against both ultraviolet A (UV-A) and ultraviolet B (UV-B) rays. The lighter your skin, the higher the SPF number should be. Generously apply the sunscreen to all exposed areas of your skin at least 30 minutes before going outdoors so that it
has time to be fully absorbed. Always reapply sunscreen immediately after swimming or every few hours if you are perspiring. Remember to put sunscreen on your ears, the back of your neck, and any bald spots on your head. Use a lip balm that contains sunscreen. Wear a wide-brimmed hat, and always wear sun- glasses that ﬁlter at least 90 percent of both UV-A and UV-B rays. Check labels for this information when you are shopping for sunglasses.
If you get a sunburn, cover the burned area with cool, clean, wet cloths or gauze, or take a cool bath or shower. Take an over-the-counter anti-inﬂamma- tory drug such as aspirin or ibuprofen to relieve pain, fever, and inﬂammation. Do not use a spray that numbs the burned area because it may cause an allergic or irritant reaction. Drink plenty of liquids and rest in a cool room for several hours. Before you expose your skin again, make sure that the inﬂammation is gone, and put extra sunscreen on the previously burned areas so you do not get burned again.
Atopic eczema is a recurrent inﬂammatory skin condition that produces redness, itching, and scaly patches. People who have atopic eczema also often have other allergic conditions, such as allergic rhinitis (see page 379) or asthma (see page
245), or are allergic to penicillin or sulfa. Atopic eczema is a very common con- dition that affects about 3 percent of Americans. The disorder can occur at any age but typically appears between infancy and young adulthood. The condition often improves on its own before puberty but also can persist throughout life.
Most people have dry skin at some point, but people with atopic eczema have periodic eruptions of red, scaly patches of skin. In adolescents and young adults the patches usually appear inside the elbows and behind the knees and at the ankles and wrists; in children they appear on the face and neck. But the eruptions can occur anywhere on the body and may not follow a pattern. The itching pro- duced by the eruptions can be severe and prolonged.
People who have atopic eczema seem to have easily irritated skin, so anything that dries or irritates the skin may trigger a ﬂare-up. They are often sensitive to low levels of humidity, and their skin condition may worsen in the winter. If this is true for you, try to bathe no more than once a day, avoid using very hot water, and use the mildest soap you can ﬁnd. After bathing, pat your skin dry; do not rub it. Immediately apply a moisturizing lotion or oil to your skin, before it has completely dried. Avoid dressing in clothes made of rough or scratchy fabrics, which can aggravate the condition. Sweating also can make the condition worse.
Depending on the severity of the condition, your doctor may refer you to a dermatologist (a doctor who specializes in treating disorders of the skin). To dis- tinguish atopic eczema from other types of skin conditions, the dermatologist will examine the skin eruptions, noting where on your body they appear and how often they occur. To control atopic eczema, the dermatologist probably will
prescribe a cream or ointment containing a corticosteroid, a drug that relieves inﬂammation. If any of the inﬂamed patches have become infected because of overly aggressive scratching, the doctor also may prescribe an antibiotic. Severe cases of atopic eczema may require treatment with ultraviolet light or oral corti- costeroid medication.
Allergic Contact Dermatitis
Allergic contact dermatitis is a skin condition that occurs when your skin comes into contact with allergens, substances to which you are allergic but that are harmless to most people. This condition is not triggered by harsh soaps or acids, for example, because these substances are irritants that will produce a rash on anyone’s skin, given enough exposure.
Upon contact with an allergen, the skin reddens and swells and may blister. The blisters may burst, leaving scaly patches. The condition is sometimes difﬁcult to distinguish from other skin conditions, such as atopic eczema (see previous page).
Substances that can trigger allergic contact dermatitis include nickel or nickel-plated items, rubber, hair dyes, and cosmetics such as perfumes and lotions. (Some people are allergic to the chemicals used to preserve cosmetics, while others are allergic to the fragrances used in these products.) Rubber can cause a more serious allergic reaction that goes beyond a simple rash. Some people who are allergic to rubber (including the latex rubber used in rubber gloves) experience itchy, watery eyes and, in some cases, shortness of breath that could lead to anaphylactic shock (see page 383), a potentially fatal allergic reac- tion. Chromium contained in cement, leather, paints, and antirust products also can produce allergic contact dermatitis. Rashes produced by plants such as poison ivy, poison oak, and poison sumac also are considered allergic contact dermatitis. People who are sensitive to poison ivy, oak, and sumac also may be allergic to the oils contained in mango skins and cashew nut shells.
To diagnose allergic contact dermatitis and to determine its cause, your doctor will examine your rash and ask questions about the materials you use at home and at work. He or she may perform a patch test, in which small amounts of sus- pected allergens are applied to your skin for a couple of days. If an area of skin becomes inﬂamed, that substance may be an allergen for you.
The rash produced by allergic contact dermatitis will usually clear up on its own once the allergen has been removed. The only way to prevent the condition from recurring is to avoid all contact with the allergen. A dermatologist can help you identify your allergens.
Seborrheic dermatitis is a common skin disorder in which red, scaly, itchy patches of skin appear where the sebaceous (oil) glands are located in the skin—
on the scalp, eyebrows, sides of the nose, behind the ears, and in the middle of the chest. The patches also can occur in the navel, under the arms, in the groin area, and on the buttocks. Extensive scratching of the itchy patches can damage the skin, producing an infection that causes the skin to become crusty and drain pus.
The disorder most commonly occurs during three stages of life: infancy (when it is known as cradle cap), middle age, and old age. People with oily skin or oily hair are susceptible to seborrheic dermatitis, and infrequent shampooing can increase the likelihood of developing the disorder. People who have acne (see below) also may develop seborrheic dermatitis. The condition seems to occur in people who have other illnesses, such as Parkinson’s disease or immune system problems. Some researchers think that a yeastlike organism may cause sebor- rheic dermatitis.
If you have seborrheic dermatitis, a dermatologist will identify the condition based on its appearance. There is no cure for seborrheic dermatitis, but it usually improves with treatment. Your doctor may recommend nonprescription med- icated shampoos that contain tar, zinc pyrithione, selenium sulﬁde, sulfur, or sal- icylic acid. A corticosteroid cream or lotion applied directly to the affected areas may also be helpful. Be sure to keep the affected areas clean and dry. Seborrheic dermatitis can recur, even with appropriate treatment.
Acne is a chronic skin disorder caused by inﬂammation of the hair follicles and the sebaceous (oil) glands in the skin. The disorder produces skin blemishes commonly called pimples. The blemishes usually appear on the face, neck, back, chest, and shoulders. Although it is not a serious condition, acne can cause scar- ring that can affect your appearance.
Acne occurs when hair follicles become blocked by plugs of sebum, the oily secretion produced by the sebaceous glands that lubricates the skin and hair. Bacteria then grow in the blocked follicles, causing inﬂammation. People with acne usually have a number of different types of blemishes, including white- heads, which appear on the skin as small, white bumps, and blackheads, which look like black spots. Other blemishes include papules, which are inﬂamed pink bumps that are tender to the touch, and pustules or pimples, which are inﬂamed, pus-ﬁlled bumps that are red at the base. Painful, inﬂamed, pus-ﬁlled bumps that are lodged deep in the skin are known as cysts; they can produce scarring.
People of any age can develop acne, but it most commonly occurs in adoles- cents. Almost 85 percent of all teenagers and young adults between ages 12 and
24 have some acne. Acne usually clears up by the time a person reaches his or her 30s, but some people in their 40s and 50s still have the condition. Acne is more common among whites.
A number of factors can contribute to the development of acne. Rising levels of male sex hormones called androgens during puberty cause the oil-producing sebaceous glands to make more sebum. Another factor appears to be heredity. The tendency to develop acne seems to run in families. Stress can aggravate the condition, as can perspiration and high levels of humidity. Friction from tight collars, backpacks, or bike helmets also can make acne worse. Picking at the blemishes can produce scarring. Certain drugs, including lithium and barbiturates, may cause outbreaks of acne. Contrary to popular belief, choco- late and greasy foods seem to have little effect on the development of acne in most people.
There is a wide range of nonprescription acne-treatment products available. Most limit the formation of new blackheads and whiteheads and reduce inﬂam- mation. The most common over-the-counter drugs used to treat acne are benzoyl peroxide, resorcinol, salicylic acid, and sulfur. These medications can produce side effects, including skin irritation, burning, or redness, but the side effects disappear when the person stops using the product.
By the time a person decides to see a doctor, he or she has probably tried sev- eral over-the-counter medications and seen little improvement. Acne may be treated by a dermatologist, but family physicians and internists also treat people who have acne. The main goal of treatment is to prevent scarring, but doctors also seek to reduce the number of blemishes and minimize the embarrassment felt by people affected with a skin disease. Drugs prescribed to treat acne address several causes: clumping of cells in the hair follicles, increased oil production, bacterial infection, and inﬂammation. Your doctor may recommend a combina- tion of medications to reach these goals.
Topical (applied to the skin) prescription drugs used to treat acne include ben- zoyl peroxide, clindamycin phosphate, erythromycin, adapalene, azelaic acid, and tretinoin. Tretinoin is a vitamin A derivative and is very effective for treating whiteheads and blackheads. Side effects from these drugs can include stinging, burning, redness, peeling, scaling, and discoloration of the skin. If you experi- ence side effects, tell your doctor as soon as possible.
For people with moderate or severe acne, doctors may prescribe oral antibi- otics in addition to a cream, lotion, or gel. Antibiotics help control acne by checking the growth of bacteria and reducing inﬂammation. They must be taken for at least 4 to 6 weeks to be effective. Some of these antibiotics may make the skin more sensitive to the sun, so you will need to take extra precautions (see page 416) when in sunlight. They also can cause upset stomach, dizziness, and skin discoloration. A doctor may prescribe a powerful medication called isotretinoin for people who have severe acne that has not responded to treatment with other acne medications. Isotretinoin can produce a number of unwanted side effects, some of which—such as increased blood cholesterol, abnormal liver enzyme levels, and birth defects—can be serious. While you are taking the drug,
your doctor will monitor the levels of glucose, cholesterol, triglycerides (fats), and liver enzymes in your blood. Discuss the risks and the beneﬁts of taking isotretinoin with your dermatologist, who can help you decide whether use of this drug is the best treatment for you.
Other treatments for acne include removal of individual blemishes, injection of a corticosteroid drug into a cyst, or a chemical peel. Cosmetic surgery (see page 439) is sometimes used to treat scarring caused by acne.
If you have acne, do not attempt to stop an outbreak or reduce oil production by aggressively scrubbing your skin or using strong soaps. This will only make the problem worse. Instead, gently wash your skin with a mild soap whenever it feels oily or greasy. And always wash your face after exercising. Your doctor can recommend the best soap or cleanser to use. Avoid squeezing, picking, or pinch- ing your skin because doing so could cause even more inﬂammation and even- tual scarring. Soften your beard with soap and water before shaving, and shave lightly to avoid nicking the blemishes. Do not try to dry out your skin or hide the blemishes by getting a suntan, because the beneﬁts are temporary at best. Expo- sure to the sun can seriously damage your skin, can promote premature aging of your skin, and can cause skin cancer. Also, many drugs used to treat acne make your skin more sensitive to the sun.
Shaving bumps or razor bumps (known medically as pseudofolliculitis barbae) is a common skin condition in the beard area of black men and others who have curly hair. The condition occurs when the sharp ends of shaved hairs grow back into the skin, causing inﬂammation. Eventually these ingrown hairs can cause scars, which resemble hard bumps, to form on the face and neck.
The only sure way to avoid developing shaving bumps is to grow a beard. If this is not practical, follow these shaving tips:
• Shave every day with a safety razor.
• Be sure to use sharp blades; replace the blades after every two shaves.
• Before shaving, gently wash your face with mild soap and a warm, soft wash- cloth; rinse your face thoroughly; and leave your face wet.
• Apply a nonirritating shaving cream or gel. Ask your doctor to recommend one.
• Always shave in the direction of hair growth.
• Do not pull or stretch your skin.
• Do not shave too closely. Press lightly with the razor. It is better for your skin if you press less ﬁrmly and shave more often.
• Do not keep going over the same spot. This can irritate your skin.
• Do not attempt to remove ingrown hairs with a tweezers. This can irritate your skin and may lead to infection.
• After shaving, rinse your face thoroughly and pat it dry.
If the condition does not clear up after trying these at-home tips, see your doctor. He or she may prescribe a cream or gel that includes a vitamin A– containing drug called tretinoin or an oral antibiotic to treat the condition.
Warning: Do not share razors. Doing so places you at risk of contracting a bloodborne infection such as hepatitis B or HIV (human immunodeﬁciency virus).
Psoriasis is a persistent skin disorder that produces red, itchy, dry patches of skin with silvery scales. The disorder often begins in childhood and comes and goes throughout a person’s life. The areas most commonly affected are the scalp, elbows, arms and legs, knees, groin and genitals, ﬁngernails and toenails, and lower back. There are several different types of psoriasis, distinguished by the shape and pattern of the scales. The most common type begins as small, red patches that grow larger and form scales.
The cause of psoriasis is unknown, but it may be linked to an abnormality in the function of white blood cells that somehow triggers inﬂammation in the skin and causes it to shed too quickly. The condition seems to run in families. Four million to 5 million people in the United States have psoriasis. Factors that can trigger the condition include bacterial or viral infections, certain drugs, dry and cold weather, sunburn, skin injury, drinking alcohol, and stress.
Doctors can diagnose psoriasis by examining the skin or by taking a sample of the skin and examining it under a microscope. The goals of treatment are to lessen inﬂammation and slow skin cell growth. A variety of different treat- ments—topical (applied to the skin) creams or lotions, light therapy, and oral medication—have been developed to reach these goals. If you have psoriasis, the treatment your doctor recommends will depend on your age, your overall health, and the severity of your condition. No treatment can cure psoriasis, but symptoms can be improved or controlled.
A common type of cream or ointment prescribed for the treatment of psoria- sis is a corticosteroid preparation (such as hydrocortisone), which is used in a weak formula for sensitive areas such as the face or the groin and in a stronger formula for other areas. Side effects of these preparations include thinning of the skin, dilation (widening) of the blood vessels, bruising, and skin-color changes. The doctor may inject a corticosteroid drug into areas that are difﬁcult to treat. Topical retinoids (such as tazarotene) are vitamin A–like medications that may be prescribed to treat mild to moderate psoriasis. Other topical psoria- sis preparations include those that contain a drug called anthralin, synthetic vita- min D, or coal tar. Many nonprescription shampoos, oils, and sprays are available to treat psoriasis on the scalp.
Both natural sunlight and artiﬁcial ultraviolet light from light boxes alter the growth of skin cells, so doctors can use light therapy to treat psoriasis. Light therapy must be used under the supervision of a doctor because excessive expo- sure to sunlight or artiﬁcial ultraviolet light can cause skin wrinkling, skin can- cer, damage to the eyes, or a ﬂare-up of psoriasis. A treatment that combines light therapy with coal tar dressings is helpful for treating severe cases of psori- asis. Another effective treatment, called PUVA (psoralens and ultraviolet A), combines ultraviolet light therapy with the oral medication psoralen.
Other medications that may be prescribed to treat psoriasis include methotrexate and oral retinoids. Methotrexate is a powerful but effective anti- cancer drug that can cause serious side effects, such as liver disease. Before a doctor prescribes methotrexate, he or she will have the person undergo a liver biopsy (a small sample of liver tissue is obtained and examined under a microscope) to make sure that the person’s liver is healthy. After the person begins taking methotrexate, the doctor carefully monitors blood levels of the drug to prevent potential problems. Retinoids (such as acitretin) may be taken alone or in combination with light therapy. Possible side effects include dry- ness of the skin, lips, and eyes; increased cholesterol levels; and formation of bone spurs.
Jock itch (known medically as tinea cruris) is a fungal infection of the groin. The fungus also can infect other areas of the body, such as the feet and the area between the toes, where it causes athlete’s foot (see next page). The infection begins as small, red spots that enlarge to form rings. At the edge of the ring the skin is raised, red, and scaly.
Jock itch is common in men who perspire heavily, who exercise vigorously in hot weather, or who are overweight. The infection can be transmitted to your groin from your feet if you have athlete’s foot and you scratch both areas. Like all tinea infections, jock itch is somewhat contagious. You can get a tinea infec- tion from wet surfaces (such as a shower stall), from another person, or even from an animal. Men who wear athletic protectors or equipment can develop a case of jock itch, especially in hot, humid weather.
If you think that you may have jock itch, see your doctor. The condition may be hard to distinguish from other skin problems that have different causes and treatments. The doctor may scrape off a small sample of affected skin and examine it under a microscope to conﬁrm the diagnosis. Jock itch is treated by applying an antifungal cream to the groin area daily for at least a month. Other tinea infections may be more difﬁcult to clear up and may require treatment with an oral antifungal medication. You will need to use all of the antifungal medica- tion prescribed—even if your skin looks and feels better—to be sure the infec- tion has been completely eliminated.