Characterization of cowhage-induced pruritus in inflamed and non-inflamed skin.

BACKGROUND AND OBJECTIVE

Pruritus is a major symptom of many inflammatory diseases and impacts greatly the quality of life in patients. We aimed to specify the characteristics of experimentally induced pruritus in normal skin and in experimentally induced inflammatory dermatitis in healthy volunteers.

METHODS

Skin inflammation was induced by the repeated application of sodium lauryl sulphate (SLS 2%) on the volar forearms of 30 healthy volunteers. Inflammatory dermatitis intensity was assessed using the eczema score adapted from Frosch and Kligman. Non-histaminergic pruritus was induced by cowhage spicules rubbed on the volar forearms and recorded for 30 min on a 10-cm visual analogue scale (VAS) in both non-inflamed and inflamed skin.

RESULTS

Induction of inflammatory dermatitis by SLS resulted in a mild inflammatory dermatitis with an inflammation score of 2.3 ± 0.1 within 7 days of treatment. Cowhage-induced pruritus was of markedly higher intensity (P < 0.001), and all but two individuals had higher maximum pruritus intensity in inflamed skin as compared to non-inflamed skin, whereas the kinetics of the pruritus response were similar. The quality of cowhage-induced pruritus was significantly different with more 'burning' and 'painful sensations' in inflamed skin (P < 0.01). Maximum pruritus intensity in inflamed skin strongly correlated with maximum pruritus intensity in non-inflamed skin (r = 0.51, P = 0.004). Skin hydration, skin barrier integrity and dermatitis severity did not correlate with pruritus intensity.

CONCLUSION

Taken together, pruritus in inflamed skin is perceived as more intense, painful and burning. This may explain, in part, why pruritus is a major driver of quality-of-life impairment in patients with chronic inflammatory skin conditions such as atopic dermatitis.

© 2019 European Academy of Dermatology and Venereology.