Cutaneous contact urticaria to pyrethrum-real?, common?, or not documented?: an evidence-based approach.

Reports suggest that pyrethrum, the insecticidally active extract from Chrysanthemum cinerariifolium, can induce Type I hypersensitivity reactions in humans. Using knowledge of pyrethrum chemistry and an evidence-based analysis of literature, whether current refined pyrethrum induces and/or elicits skin manifestations of contact urticaria was assessed. Current extraction and refinement techniques suggest that refined pyrethrum lacks the presence of significant, if any, proteins speculated to induce Type I hypersensitivity. Our interpretation suggests that no reports of Type I reactions presented in the literature fulfill the criteria for immunologic contact urticaria. Future patient testing with current commercial material should clarify its Type I immunologic potential, if any.