Skin Disorders And Cutaneous Drug Reactions
The word dermatitis is a general term denoting an inflammatory erythematous rash. The disorders discussed in this chapter include contact dermatitis, seborrheic dermatitis, diaper dermatitis, and atopic dermatitis. Drug-induced skin disorders have been associated with most commonly used medications and may present as maculopapular eruptions, fixed-drug eruptions, and photosensitivity reactions.
- Contact dermatitis is an acute or chronic inflammatory skin condition resulting from contact of an inciting factor with the skin. In allergic contact dermatitis, an antigenic substance triggers Langerhans cells, and their immunologic responses produce the allergic skin reaction, sometimes several days later. Irritant contact dermatitis is caused by an organic substance that usually results in a reaction within a few hours of exposure.
- Diaper dermatitis (diaper rash) is an acute, inflammatory dermatitis of the buttocks, genitalia, and perineal region. The reaction is a type of contact dermatitis, as it results from direct fecal and moisture contact with the skin in an occlusive environment.
- Atopic dermatitis is an inflammatory condition with genetic, environmental, and immunologic mechanisms. Many immune cells have demonstrated abnormalities, including Langerhans cells, monocytes, macrophages, lymphocytes, mast cells, and keratinocytes.
- Drug-induced cutaneous reactions tend to be immunologic in origin and relate to hypersensitivity, but some reactions are nonallergic. The pathogenesis of fixed-drug reactions is not well understood.
- Drug-induced photosensitivity reactions are divided into phototoxicity (a nonimmunologic reaction) and itphotoallergic reactions (an immunologic reaction). The latter form is far less common. Medications associated with photosensitivity reactions include fluoroquinolones, nonsteroidal anti-inflammatory drugs, phenothiazines, antihistamines, estrogens, progestins, sulfonamides, sulfonylureas, thiazide diuretics, and tricyclic antidepressants.
- Patient age and hormonal status in women should be considered in the initial evaluation of patients with skin disorders. Older patients are predisposed to developing psoriasis, seborrhea, and other skin conditions. Atopic dermatitis is most likely to occur in children. Menopausal women tend to develop brown hyperpigmentation, or melasma. Pregnant women may develop hyperpigmentation of the areola and genitalia as well as melasma.
- Patients presenting with a rash or skin lesion should be evaluated for potential anaphylaxis or angioedema (e.g., symptoms of difficulty in breathing, fever, nausea, vomiting).
- The area involved and the number of lesions present are important considerations. A rash involving only the arms and legs suggests a nonsystemic cause, whereas involvement of the arms, legs, and trunk indicates a systemic cause.
- Lesions should be inspected for color, texture, size, and temperature. Areas that are oozing, erythematous, and warm to the touch may be infected.
- The duration of the skin condition should be determined, and the temporal relationship with any new medications should be established.
- Assessment for potential drug-induced skin disorders begins with a comprehensive medication history, including episodes of previous drug allergies.
- Initial treatment should focus on identification and removal of the offending agent.
- Products that relieve itching, rehydrate the skin, and decrease the weeping of lesions provide some immediate relief.
- In the acute inflammatory stage, wet dressings are preferred because ointments and creams further irritate the tissue.
- Astringents such as aluminum acetate or witch hazel decrease weeping from lesions, dry out the skin, and relieve itching. They are applied as wet dressing for no longer than 7 days.
- For chronic dermatitis, lubricants, emollients, or moisturizers should be applied after bathing. Soap-free cleansers and colloidal oatmeal products also alleviate itching and soothe the skin.
- If the reaction does not subside within a few days, topical corticosteroids may be needed.