Dermatophyte infections can complicate atopic dermatitis and may contribute to exacerbation of disease activity. Elevated serum IgE levels to both trichophytic antigens and to Pityrosporum ovale , a lipophilic yeast, have been reported. Infestation with scabies should also be considered in the differential diagnosis of flaring atopic dermatitis, and can be diagnosed with skin scrapings examined under the microscope. Antihistamines Pruritus is the most common, but often least tolerated symptom of atopic dermatitis. Antihistamines primarily act by blocking the H1 receptors in the dermis and thereby ameliorate histamine-induced pruritus.
Histamine is, however, only one of many mediators that can induce pruritus of the skin.
Some antihistamines are mild anxiolytics and may offer symptomatic relief through tranquilizing and sedative effects. Antihistamine therapy may be useful in some patients for control of pruritus. Since pruritus is usually worse at night, the sedating antihistamines, eg, hydroxyzine or diphenhydramine, may offer an advantage with their soporific side effects when used at bedtime. It can be used in doses of 10 to 75 mg orally at night or 75 mg to 150 mg in divided doses throughout the day in adult patients. If nocturnal pruritus remains severe, short-term use of a sedative to allow adequate rest may be appropriate.