TREATMENT OF AQUAGENIC PRURITUS WITH TOPICAL CAPSAICIN CREAM

Background: Aquagenic pruritus is characterized by pruritus after cont act with water; there are no objective cutaneous changes. Capsaicin, w hich induces the release of neuropeptides from A delta and C cutaneous nerve fibers, has been successfully used in the treatment of several dermatoses associated with pruritus. Among the many different neuropep tides present in human skin, the undecapeptide substance P has been sh own to cause pruritus. Objective: We evaluated the clinical effect and searched for alterations in cutaneous neuropeptidergic fibers before and after treatment with capsaicin cream. Methods: Five patients with aquagenic pruritus were treated with capsaicin cream 0.025%, 0.5% or 1 .0% three times daily for 4 weeks. Direct immunofluorescence (DIF) was performed before and after treatment to evaluate the storage of neuro peptides in the A delta and C type cutaneous nerve fibers. Results: Be fore treatment (when by DIF the neuropeptidergic fibers appeared fille d with neuropeptides), contact with water consistently provoked itchin g. After capsaicin treatment (when by DIF the neuropeptidergic fibers were depleted of neuropeptides), contact with water did not evoke prur itus. Areas of skin treated with the vehicle alone showed no clinical improvement or change in neuropeptide content. Conclusion: This study suggests that neuropeptides, including substance P, may contribute to mediating the itch in aquagenic pruritus.