Deworming is not a risk factor for the development of atopic diseases: a longitudinal study in Cuban school children.

BACKGROUND: Soil-transmitted helminth (STH) infections have been suggested to protect from allergic sensitization and atopic diseases. Consequently, anthelminthic treatment would increase the prevalence of atopic disease in STH endemic populations. OBJECTIVE: To investigate the effect of deworming on allergic sensitization and atopic diseases in Cuban schoolchildren. METHODS: We followed up 108 STH positive schoolchildren aged 5-13 in six-monthly intervals for 24 months. Four consecutive groups of, respectively, 104, 56, 68, and 53 STH positive children were used as 'untreated' reference groups to assess general time trends. STH infections were diagnosed by stool examination. Asthma, allergic rhinoconjunctivitis, and atopic dermatitis were diagnosed by International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire and allergic sensitization by skin prick testing (SPT). At each time point, STH positive children were treated with one single dose of 500 mg mebendazole. RESULTS: After deworming, the frequency of asthma significantly decreased (P < 0.001) while the frequency of allergic rhinoconjunctivitis and atopic dermatitis was not affected (P = 0.129 and P = 0.751, respectively). The percentage of SPT positives temporarily increased (P < 0.001) and subsequently returned to nearly baseline values (P = 0.093). In the references groups, no change over time was observed in the proportion of children with allergic sensitization and atopic diseases (P > 0.05). CONCLUSION & CLINICAL RELEVANCE: Our results indicate that atopic diseases do not increase after anthelminthic treatment. Allergic sensitization on the other hand increases after deworming. As this increase appears only temporarily, deworming of schoolchildren does not seem to be a risk factor for the development of allergic sensitization, nor for atopic diseases.