Treatment of aquagenic pruritus with topical capsaicin cream.
BACKGROUND
Aquagenic pruritus is characterized by pruritus after contact with water; there are no objective cutaneous changes. Capsaicin, which 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 neuropeptides present in human skin, the undecapeptide substance P has been shown 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 neuropeptides in the A delta and C type cutaneous nerve fibers.


RESULTS
Before treatment (when by DIF the neuropeptidergic fibers appeared filled with neuropeptides), contact with water consistently provoked itching. After capsaicin treatment (when by DIF the neuropeptidergic fibers were depleted of neuropeptides), contact with water did not evoke pruritus. Areas of skin treated with the vehicle alone showed no clinical improvement or change in neuropeptide content.


CONCLUSIONS
This study suggests that neuropeptides, including substance P, may contribute to mediating the itch in aquagenic pruritus.
Lotti
T
T
Department of Dermatology, University of Siena, Italy.
Teofoli
P
P
Tsampau
D
D
D000287:Administration, Topical; D002211:Capsaicin / Q000008:administration & dosage / Q000627:therapeutic use*; D004311:Double-Blind Method; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D008297:Male; D009412:Nerve Fibers / Q000737:chemistry; D009479:Neuropeptides / Q000032:analysis; D011537:Pruritus / Q000188:drug therapy* / Q000209:etiology; D012867:Skin / Q000294:innervation; D013373:Substance P / Q000032:analysis; D014867:Water / Q000009:adverse effects*
D009479:Neuropeptides; D014867:Water; D013373:Substance P; D002211:Capsaicin