Tuberculosis and atopy: a study in an endemic area

Atopy is expected to be less frequent and milder in patients with early exposure to bacterial infections because of regulatory immune mechanisms. The definition of the hygiene hypothesis and most of the related studies have been performed in children. In a population where both tuberculosis (tbc) and atopy are prevalent, we investigated skin test results to allergens in adults with tbc. A standard panel of skin-prick tests (SPTs) was applied to patients with active (n = 21) or inactive (n = 72) tbc and age-matched healthy control subjects (n = 76) from the same environment. Patients also had tuberculin skin tests applied twice at 8 weeks' interval. Patients with inactive tbc had a higher rate of allergic symptoms than those with active tbc (P < 0.01). SPTs were less frequently positive in tbc patients than in control subjects (P < 0.005). Tuberculin skin reactions were not related to SPTs positivity. Our results suggest allergic skin test reactions may be suppressed in patients with tbc: the interpretation of SPTs should be made accordingly.