Antipruritic effect of pretreatment with topical capsaicin 8% on histamine- and cowhage-evoked itch in healthy volunteers: a randomized, vehicle-controlled, proof-of-concept trial

Abstract

Topical capsaicin 8% pretreatment for 24 h reduced histaminergic and nonhistaminergic itch by about 75%, while a significant reduction (≈60%) was achieved for only nonhistaminergic itch in a standard 1-h treatment. Further investigations are needed to elucidate the clinical potential of high-concentration capsaicin as an antipruritic.

UVB‐ andNGF‐induced cutaneous sensitization in humans selectively augments cowhage‐ and histamine‐induced pain and evokes mechanical hyperknesis

“…Secondly, the optimal force range for evoking mechanical itch using von Frey filaments appears to correspond to that of human polymodal C‐fibre activation recorded by microneurography while being insufficient in evoking pain . Thirdly, mechanical itch sensitivity is partially reduced in human skin where intraepidermal capsaicin‐sensitive fibres have been defunctionalized . The mechanisms behind the development of hyperknesis for both the UVB and NGF models are hitherto unexplored, but the differential time courses of the two models suggest that the mechanisms are dissimilar.…”

“…Currently, the only known human cutaneous sensitization model also capable of evoking increased itch sensitivity to both mechanical and chemical provocations is the squaric acid dibutyl ester model of allergic contact dermatitis which also give rise to substantial spontaneous itch, mild pain and prolonged skin lesions . The techniques applied in the present study to detect increased itch sensitivity to chemical and mechanical provocation can feasibly be applied to assess itch sensitization in chronic itch patients or in proof‐of‐concept studies on novel antipruritics . However, the potential clinical implications of such tests as diagnostic or treatment responsiveness biomarkers remain to be explored …”

Antipruritic effects of transient heat stimulation on histaminergic and nonhistaminergic itch

“…This procedure was performed for approximately 10 s and was confirmed by the participants, who were prompted to report the sensation of several tiny pricks (caused by the immediate insertion and indicating that the spicules were successfully penetrating the epidermis). This method of cowhage administration has been used in several previous studies . The itch elicitation techniques were identical for both experiments.…”

“…This method of cowhage administration has been used in several previous studies. 12,13 The itch elicitation techniques were identical for both experiments.…”

Topical capsaicin 8% for the treatment of neuropathic itch conditions

“…Recent experimental studies indicate that prolonged application (> 60 min) can vastly improve the effect of topical capsaicin 8%. In fact, a very recent experimental study showed that human skin can be rendered almost completely devoid of pruriceptive responsiveness to the two most commonly studied pruritogens (histamine and cowhage) following prolonged capsaicin 8% treatment . This indicates that high‐concentration capsaicin may be useful not only for the treatment of neuropathic itch, but also for more common itch conditions of dermatological origin.…”