Background: Some studies have reported an increase of atopy in HIV-infected (HIV+) patients, but the cause still remains unclear., Objective: To determine the prevalence of atopy in HIV+ patients and to investigate its predictors., Methods: Seventy-four HIV+ hospitalized patients (46 of them with AIDS) were studied prospectively for the presence of atopy, based on immediate hypersensitivity to common allergens by prick test. Serum immunoglobulins, specific IgE, lymphocyte subsets, and the expression of low affinity IgE receptor (CD23) on B cells were determined., Results: Thirty-one percent of patients presented IgE values greater than 150 ku/L (39% of patients without AIDS and 26% of AIDS patients; P = .23) and 47% showed an increase (> or = 2%) in the percentage of CD23+ B cells. Non-AIDS patients had higher IgE values than AIDS patients (346 +/- 605 versus 175 +/- 276; P = .16). Atopy prevalence was higher in non-AIDS than in AIDS patients (28% versus 11%; P = .06). Specific IgE agreed with positive prick test in 58% of cases. Multivariate analysis showed that a personal history suggestive of allergic disease and IgE > 150 ku/L were predictors of atopy, while gender, risk group, CD4+ T cells, CD23 expression on B cells, and AIDS were not associated., Conclusions: HIV+ patients present a higher prevalence of atopy in early stages of HIV infection than general population. Since allergic reactions could accelerate HIV-infection by increasing type 2 cytokines, it is important to evaluate the atopic state in HIV+ patients with IgE > 150 ku/L or with suggestive allergic history in order to prevent it.