Effect of shaving on axillary stratum corneum

Removal of underarm hair is an intrinsic part of the care regimen for the majority of female consumers, with most using a wet shave with a disposable razor. However, little is known of the impact of shaving on axillary skin, and it is a particularly neglected area of research. To investigate this, we have studied the acute and chronic effects of shaving ultrastructurally, biochemically and functionally. A forearm patch test protocol was devised for antiperspirant (AP) product screening, which involved a pre-shave of the test site with a dry razor just prior to patching. Comparison of the irritation caused by a series of AP products confirmed that shaving leads to increased irritation consistent with enhanced sensitivity. The effect of regular shaving in the axilla was assessed in a 4-week in-use study with shaving either once a week or once a day, both combined with the application of an AP. Expert visual assessment of skin condition showed that more frequent shaving promoted a higher level of visible irritation. However, indirect measurement using corneosurfametry indicated no significant changes to the lipid barrier over the study period irrespective of shaving frequency. Nevertheless, digital images of the axillary skin after dry shaving show distinct opaque lines because of uplifting skin flakes with a corresponding increase in scaliness parameter. Moreover, histamine iontophoresis to assess skin sensitivity demonstrated a significant enhancement of histamine-induced itch and neurogenic flare.