surface of the skin and inspecting the site for inflammation 48–72 hours later.

The treatment of contact dermatitis follows three key principles: (1) continued contact with the specific allergen must be avoided by all means, (2) local irritation should be avoided, and (3) local therapy should be employed. (Steroid creams are generally prescribed, with oral steroids used in the most severe cases.)

Prevalence Contact dermatitis accounts for 20–30 percent of all patients treated in dermatology clinics. Seasonal factors such as the growth of poison ivy alter the rates of dermatitis cases. Most of the allergens associated with contact dermatitis are not aeroallergens; however, there have been instances in which airborne contact allergens have produced contact dermatitis.

Less Common Diseases Clearly Related to Allergy

Allergic bronchopulmonary aspergillosis, hypersensitivity pneumonitis, and humidifier fever are conditions that appear to be less common in the United States than the diseases discussed previously in this chapter. Nevertheless, they merit attention because of their potential severity.

ALLERGIC BRONCHOPULMONARY ASPERGILLOSIS

Allergic bronchopulmonary aspergillosis (ABPA) is an intriguing condition characterized by the development of a specific immune response to the Aspergillus species of fungi that colonize the central airways. A related disease is allergic Aspergillus sinusitis. The diagnostic features of the disease include (1) asthma, (2) a history of infiltrates found by chest radiograph, (3) immediate skin test reactivity to Aspergillus, (4) elevated total serum IgE, (5) precipitating antibodies to Aspergillus fumigatus, (6) peripheral blood eosinophilia (expected at the time of radiographic infiltrates), (7) elevated serum IgE and IgG to A. fumigatus, and (8) proximal (central) bronchiectasis (Greenberger, 1988).

Prevalence

An estimated 10,000 cases of ABPA were prevalent in the United States in 1977; it is thought to be more common in the United Kingdom (NIAID, 1979). Approximately 25 percent of patients with asthma have IgE antibody to Aspergillus flavus, and 10 percent have IgG antibody; yet ABPA occurs in only 4 percent of Aspergillus skin test-positive individuals (Schwartz et al., 1978). ABPA also occurs in 10 percent of patients with cystic fibrosis (Greenberger, 1988).



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