Irritants will show a response in a few hours. If irritation occurs, the substance may be falsely identified, which is the major weakness of this test. Histologically, appearance varies with the clinical spectrum of the disease. With mild contact dermatitis, simple parakeratosis and hyperkeratosis with intracellular edema and small infiltrates are seen. With chronic disease, ballooning degeneration and frank necrosis may be appreciated.
Hyperpigmented lesions show melanin-laden macrophages in the upper dermis with basal pigmentation.
This may be impossible because of a patient's work environment or economic situation. Clothing to limit exposure may be useful. Harsh soaps and detergents should be avoided. Sweating and cold weather may cause exacerbations. Irritating fabrics and scratching also are problematic.