Dermatitis

Dermatitis is a skin eruption that is caused by medications (drug-induced dermatitis) or by a chemical agent coming in touch with the skin (contact dermatitis).

Drug-induced dermatitis is characterized by skin lesions that can be a rash, urticaria, papules, vesicles or life-threatening skin eruptions such as erythema multiforme (red blisters over a large portion of the body) or Stevens-Johnson syndrome (large blisters in the oral and anogenital mucosa, pharynx, eyes, and viscera). As a result of having a hypersensitive reaction to a drug, the patient may form sensitizing lymphocytes.

If the patient received multiple drug therapy, the last drug administered to the patient may have caused hypersensitivity and skin eruptions. Drug-induced dermatitis may take a few minutes, several hours, or a day for urticaria (hives) to appear. Certain drugs such as penicillin are known to cause hypersensitivity.

Other drug-induced dermatitis includes discoid lupus erythematosus (DLE) and exfoliative dermatitis. Hydralazine hydrochloride (Apresoline), isoniazid (INH), phenothiazines, anticonvulsants, and antidysrhythmics such as procainamide (Pronestyl) may cause lupus-like symptoms. If lupus-like symptoms occur, the drug should be discontinued.

Certain antibacterials and anticonvulsants may cause exfoliative dermatitis, resulting in erythema of the skin, itching, scaling, and loss of body hair.

Contact dermatitis, also called exogenous dermatitis, is caused by chemical or plant irritation and is characterized by a skin rash with itching, swelling, blistering, oozing, or scaling at the affected skin sites. The chemical contact may include cosmetics, cleansing products (soaps and detergents), perfume, clothing, dyes, and topical drugs. Plant contacts include poison ivy, poison oak, and poison sumac.

Nonpharmacological treatment of contact dermatitis includes avoiding direct contact with the causative irritant. The patient should use protective gloves and clothing if the chemical agent is associated with his or her employment.

At the first sign of contact dermatitis, clean the skin area immediately. Patch testing may be needed to determine the causative factor. Apply wet dressings containing Burow's solution (aluminum acetate), lotions such as calamine that contain zinc oxide, calcium hydroxide solution, and glycerin. Calamine lotion may contain the antihistamine diphenhydramine and is used primarily for plant irritations. If itching persists, antipruritics (topical or systemic diphenhydramine [Benadryl]) may be used. Topical antipruritics should not be applied to open wounds or near the eyes or genital area.

Other medications used as antipruritics are:

• Systemic drugs such as cyproheptadine hydrochloride (Periactin) and trimeprazine tartrate (Temaril).

• Antipruritic baths of oatmeal such as Alpha-Keri.

• Solutions of potassium permanganate, aluminum subacetate, or normal saline.

• Glucocorticoid ointments, creams, or gels.

Topical glucocorticoids can aid in alleviating dermatitis (see Table 20-2). These include dexamethasone (Decadron) cream, hydrocortisone ointment or cream, methylprednisolone acetate (Medrol) ointment, triamcinolone acetonide (Aristocort), and flurandrenolide (Cordran).

Topical glucocorticoids are systemically absorbed into the circulation depending on whether it is a cream or lotion, drug concentration, drug composition, and skin area to which the glucocorticoid is applied.

Absorption is greater at the face, scalp, eyelids, neck, axilla, and genitalia with prolonged use of the topical drug and if the drug is continuously covered with a dressing. Prolonged use of topical glucocorticoids can cause thinning of the skin with atrophy of the epidermis and dermis, and purpura from small-vessel eruptions.

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