Human skin capsaicin effect

While capsaicinoids may have a vesicant effect, depending on length of exposure, in most cases it produces a burning sensation and mild erythema. Capsaicins cause erythema and burning pain without vesiculation when applied topically to human skin (Smith et al, 1970 Burnett, 1989 Watson et al, 1996 Herman et al, 1998). Skin blistering and rash may occur after chronic or prolonged capsaicin exposures (Morton, 1971). 

Smith, J.G., Jr., Crounse, R.G., Spence, D. (1970). The effects of capsaicin on human skin, liver and epidermal lysosomes. J. Invest. Dermatol. 54 170-3. 

Bunker, C.B., Cerio, R., Bull, H.A., Evans, J., Dowd, P.M., Foreman, J.C. (1991). The effect of capsaicin application on mast cells in normal human skin. Agents Actions 33 195-6. 

Nicolazzo et al. [52] considered the use of the lipophilic skin penetration enhancers, octisalate and padimate (both used in sunscreens), in comparison to Azone on the buccal absorption of various drugs in vitro. They were found to have limited effect in enhancing the permeation of triamcinolone acetonide (although some increase in tissue uptake was proposed in some cases) relative to Azone, while reducing the penetration of estradiol and caffeine. One interesting report is that of the effect of capsaicin from capsicum, a commonly used food ingredient, which has been reported to enhance the permeability of sulfathiazole in human volunteers [53] presumably by a direct irritation effect on the mucosa. This raised an interesting issue of the effect of diet on oral mucosal permeability. 

Exposure to other RCAs causes similar dermal effects. CN is a more potent irritant than CS. In a human study involving dermal application, CN (0.5 mg) powder caused irritation and erythema when on the skin for 60 min (Holland and White, 1972). It took 20 mg CS to cause similar effects for the same duration of exposure. Exposure to 5% capsaicin pepper spray causes immediate and severe erythema and edema in the skin (Herman et al, 1998). Similarly, pepper ball pellets fired at individuals will cause erythema, pain, and edema at the site of impaet. The initial point of contact may become infected, scar, or heal with hyperpigmentation (Hay et al, 2006). 

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