Silk-induced asthma in children: a report of 64 cases.

A total of 64 children less than 15 years of age with asthma caused by silk were studied. The diagnosis was based on a history of wheezing, positive skin tests to silk, positive conjunctival or nasal provocation tests, or serum IgE-Sw (silk waste). The average age of onset was 4 years 2 months. Sex ratio (M:F) was 3.6:1. A positive skin test is essential for the diagnosis. Conjunctival provocation tests were performed in 80% of cases because of reliability, safety, and convenience. The first symptom appeared an average of 10 months after initial exposure to silk. In 61% of patients, asthma was accompanied by allergic rhinitis but in only 14% of cases by conjunctivitis. In most cases, asthma occurred in winter, due to seasonal use of bed quilts or clothes filled with silk. Silk is a highly potent allergen. The average mean wheal diameter elicited by silk in prick testing was larger than two histamine equivalent prick tests. A cross reactivity exists among mulberry silk, and silkworm cocoons, batryticated silkworms, and silkworm chrysalis.