Skin

Most skin complaints are not serious, but they may be distressing if visible. They include infection, inflammation and irritation, infestation by skin parasites, and changes in skin structure and texture (psoriasis and acne).

Antipruritic medications

Itching (irritation of the skin that creates the urge to scratch), also known as pruritus, probably occurs as a result of chemical changes in the skin caused by disease, allergy, inflammation, or exposure to irritant substances. People differ in their tolerance of itching, and an individual's threshold can be altered by stress and other psychological factors.

Itching is a common symptom of many skin disorders, including eczema and allergic conditions such as urticaria (hives). It may also be caused by localized fungal infection or parasitic infestation. Diseases such as chicken pox and psoriasis may also cause itching. Itching may also occur in diabetes mellitus, jaundice, and kidney failure.

In many cases, generalized itching is caused by dry skin. Itching in particular parts of the body often has special causes: itching around the anus (pruritus ani) may result from hemorrhoids or worm infestation, genital itching in women (pruritus vulvae) may be caused by vaginal infection or, in older women, hormone deficiency.

Although scratching provides temporary relief, it often increases skin inflammation and thus may make the condition worse. In some cases, continued scratching of an area of irritated skin can lead to a vicious circle of scratching and itching that continues long after the original cause of the trouble has been removed.

A number of different types of medication are used for the relief of skin irritation. These include soothing preparations that are applied to the affected skin and medicaments that are taken by mouth. The principal medicaments used in antipruritic medications include corticosteroids, local anesthetics, and antihistamines. Plain emollient or cooling creams and ointments containing no active ingredients are often recommended.

The main risk with any of these preparations other than simple emollient and soothing preparations is that prolonged or heavy use may cause skin irritation, thereby aggravating itching. Antihistamine and local anesthetic creams are especially likely to irritate or cause allergic reactions. If this occurs, stop therapy. Antihistamines taken by mouth to relieve itching are likely to cause drowsiness.

Because itching can be a symptom of many underlying conditions, self-treatment should be continued for no longer than a week before seeking medical advice.

Topical corticosteroids

Corticosteroid medicaments (often simply called steroids) are related to hormones produced by the adrenal glands. Topical preparations containing a corticosteroid medicament are often used to treat skin conditions in which inflammation is a prominent symptom.

Corticosteroids prevent the release of chemicals that trigger the symptoms of inflammation. Conditions for which topical corticosteroids are prescribed improve within a few days of starting treatment. Applied topically, corticosteroids rarely cause adverse effects, but the stronger medicaments carry certain risks when used in high concentrations.

Prolonged use of potent corticosteroids in high concentrations can lead to permanent changes in the skin. The most common effect is thinning of the skin, sometimes resulting in stretch marks that may be permanent. Fine blood vessels under the surface of the skin may become prominent (a condition known as telangiectasia). The vessels may become damaged, resulting in a red rash beneath the skin. Because the skin on the face is especially vulnerable to such damage, only weak corticosteroids are sometimes prescribed for use on the face. Dark-skinned people sometimes suffer a temporary reduction in pigmentation at the site of application.

When powerful corticosteroid preparations have been used for a prolonged period, abrupt discontinuation of the treatment can result in a general reddening of the skin called "rebound erythroderma." This may be avoided by a gradual reduction in dosage. Corticosteroids suppress the body's immune system, thus increasing the risk of infection. For this reason, they are not used alone to treat skin inflammation caused by bacterial or fungal infection. However, they may sometimes be included in a topical preparation that also contains an antibiotic medicament or antifungal agent.

Anti-infective skin preparations

The skin is the body's first line of defense against infection. Yet it can also become infected itself, especially if the outer layer (epidermis) is damaged by a burn, cut, scrape, insect bite, or an inflammatory skin condition such as eczema or dermatitis. Several different types of organism may infect the skin, including bacteria, viruses, fungi, and yeasts.

Some ointments containing antibiotics are available without prescription, but physicians do not encourage the use of these preparations for self-medication because of the risk of encouraging the formation of medicament-resistant strains of bacteria if an inappropriate medication is used. Seek medical advice if you suspect that a wound or other skin condition has become infected, and follow your physician's instructions concerning the duration of treatment even though the infection may appear to have cleared.

Any topical antibiotic product can irritate the skin or cause an allergic reaction. Irritation is sometimes caused by another ingredient of the preparation rather than the active medicament, for example, a preservative contained in the preparation. Allergic reactions causing swelling and reddening of the skin are more likely to be caused by the antibiotic itself. Any adverse reaction of this kind should be reported to your physician, who may substitute another medicament, or prescribe a different preparation.

Medicaments to treat parasites

Mites and lice are the most common parasites that live on the skin. Mites cause the skin disease known as scabies; they burrow into the skin and lay eggs, causing an intense itching. Scratching the affected area results in bleeding and the formation of scabs, and increases the risk of infection.

There are three types of lice, each of which infests a different part of the body: the head louse, the body (or clothes) louse, and the crab louse, which often infests the pubic areas but is also sometimes found on other hairy areas such as the eyebrows. All lice cause itching and lay eggs (nits) that look like white grains attached to hairs.

Both mites and lice are passed on by direct contact with an infected person (during sexual intercourse in the case of pubic lice) or, particularly in the case of body lice, by contact with infected bedding or clothing.

The medicaments most commonly used to eliminate skin parasites are insecticides that kill both the adult insects and their eggs. The principal medicaments are permethrin and lindane (both scabies and louse infestations), crotamiton (scabies only), and a combination of pyrethrins and piperonyl butoxide (louse infestations only). Scabies infestations are usually treated by applying a preparation containing permethrin, lindane, or crotamiton as instructed by the leaflet with the preparation.

One or two treatments are normally sufficient to remove the scabies mites. However, the itch associated with scabies may persist after the mite has been removed, so it may be necessary to use a soothing cream or medication containing an antipruritic medicament to ease this. People who have skin-to-skin contact with a sufferer from scabies -family members and sexual partners -should also undergo treatment with antiparasitic preparations at the same time.

Head and pubic lice infestations are usually treated by applying a preparation of one of the products, and washing it off with water as instructed by the leaflet with the preparation. If the skin has become infected as a result of scratching, a topical antibiotic may also be prescribed.

Preparations prescribed to control parasites can cause irritation and stinging that may be intense if the medication is allowed to come into contact with the eyes, mouth, or other moist membranes. Care is therefore needed when applying these preparations. Because they are applied topically, antiparasitic medicaments seldom have generalized effects. Nevertheless, it is important not to apply these preparations more often than directed and to keep them well out of the reach of children at all times.

Medicaments to treat acne

Acne, known medically as acne vulgaris, is a common condition caused by an excess production of the skin's natural oil (sebum), which leads to blockage of hair follicles. Though it chiefly affects adolescents, acne may occur at any age as a result of taking certain medicaments, exposure to industrial chemicals, oily cosmetics, or hot and humid conditions.

Acne primarily affects the skin on the face, neck, back, and chest. The principal skin symptoms are blackheads, papules (inflamed spots), and pustules (raised pus-filled spots with a white center). Mild acne may produce only blackheads and an occasional papule or pustule. Moderate cases are characterized by larger numbers of pustules and papules. In severe cases of acne, painful, inflamed cysts also develop. These can sometimes cause permanent pitting and scarring of the skin.

Medication for acne can be divided into two groups: topical preparations applied directly to the skin and systemic treatments taken by mouth.

Medicaments used to treat acne act in different ways. Some have a keratolytic effect, that is, they loosen the dead cells on the skin surface. Other medicaments counter bacterial activity in the skin or reduce sebum production.

Topical anti-acne preparations containing medicaments such as benzoyl peroxide, salicylic acid, tretinoin, and sulfur, have a keratolytic effect. Benzoyl peroxide and sulfur also have an antibacterial effect. Antibiotics applied topically or taken systemically reduce bacterial activity, but may also have a direct anti-inflammatory effect on the skin. Isotretinoin reduces the production of sebum, soothes inflammation, and also helps to unblock hair follicles.

Keratolytic preparations often cause soreness of the skin, especially at the start of treatment. If this persists, a change to a milder preparation may be recommended. Day-to-day side effects are rare with antibiotics.

Isotretinoin treatment often causes dryness and scaling of the skin, particularly on the lips. The skin may become itchy and some hair loss may occur.

Antibiotics applied topically may, in rare cases, provoke an allergic reaction requiring discontinuation of treatment. The tetracyclines, some of the most commonly used antibiotics for acne, are not suitable for use by mouth in pregnancy since they can discolor the teeth of the developing baby. Isotretinoin can increase levels of fat in the blood. More seriously, the medicament may cause major abnormalities of the developing baby if taken during pregnancy. Women taking this medicament must be certain to use effective contraception.

Medicaments for psoriasis

The skin is constantly being renewed; as fast as dead cells in the outermost layer (epidermis) are shed, they are replaced by cells from the base of the epidermis. Psoriasis occurs when the production of new cells increases while the shedding of old cells remains normal. As a result, the live skin cells accumulate and produce patches of inflamed, thickened skin covered by silvery scales. In some cases, the area of skin affected is extensive and causes severe embarrassment and physical discomfort. Psoriasis may occasionally be accompanied by arthritis in which the joints become swollen and painful.

The underlying cause of psoriasis is unknown. It usually first occurs between the ages of 10 and 30, and recurs throughout life. Outbreaks may be triggered by emotional stress, skin damage, and physical illnesses. Psoriasis can also be a consequence of the withdrawal of corticosteroid medicaments.

There is no complete cure for psoriasis. Simple measures such as careful sunbathing or using an ultraviolet lamp may help to clear mild psoriasis. An emollient cream often soothes the irritation. When such measures fail to provide adequate relief, additional medicament therapy is needed.

Anthralin, etretinate, and methotrexate slow down the rapid rate of cell division that is responsible for skin thickening. Acitretin and etretinate also reduce production of keratin, the hard protein that forms in the outer layer of skin. Salicylic acid and coal tar remove the layers of dead skin cells. Corticosteroids reduce inflammation of the underlying skin.

Appropriate treatment usually improves the appearance of the skin. However, because medicaments cannot cure the underlying cause of the disorder, psoriasis tends to recur even after successful treatment.

Individual medicaments may cause side effects. Topical preparations can cause stinging and inflammation, especially if applied to normal skin. Coal tar and methoxsalen increase the skin's sensitivity to sunlight; excessive sunbathing or over exposure to artificial ultraviolet light may damage skin and worsen the condition.

Acitretin and etretinate may damage the developing baby if taken during pregnancy. Women taking these medicaments must use effective contraception. Both agents can also damage the liver. Methotrexate can cause gastrointestinal upsets and bone marrow damage. Topical corticosteroids may also cause rebound worsening of psoriasis when stopped.

Sunscreens

Sunscreens are chemicals usually formulated as creams, lotions, or oils, that protect the skin from the damaging effects of ultraviolet radiation from the sun. People vary widely in their sensitivity to sunlight. Fair-skinned people generally have the least tolerance to direct sunlight and tend to burn easily, while people with darker skin can usually withstand exposure to the sun for much longer periods without suffering noticeable harm.

In a few cases the skin is made more sensitive to sunlight by a disease such as pellagra (a form of malnutrition primarily due to a deficiency of niacin) or herpes simplex infection. Certain medicaments -such as the thiazide diuretics, phenothiazine anti psychotics, sulfonamide anti- bacterials, quinolone and tetracycline antibiotics, psoralens, and coal tar -can also increase the skin's sensitivity to sunlight.

Sunlight is composed of different wavelengths of electromagnetic radiation. Of these, ultraviolet radiation can be particularly harmful to the skin. The chemicals in sunscreens absorb ultra-violet radiation, ensuring that a smaller proportion of it reaches the skin.

Sunscreens only form a physical barrier to the passage of ultraviolet radiation. They do not alter the skin to make it more resistant to sunlight. Therefore a sunscreen lotion must be applied frequently to maintain protection.

Even sunscreens with the highest blocking effect do not completely exclude radiation from the sun. Accordingly, people who are fair-skinned or very sensitive to sunlight should never expose themselves to direct sun, even if they are using a sunscreen.

Sunscreens can irritate the skin and some may cause an allergic rash. People who are sensitive to medicaments such as procaine and benzocaine, certain hair dyes, and sulfonamides, may develop a rash following application of a preparation containing para-aminobenzoic acid (PABA) or benzophenones such as oxybenzone.

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