# Effects of Stimulus Temperature and Skin Hydration Levels on Wetness Perception at the Underarm

## TL;DR

This study explores how temperature and skin hydration affect how wet the underarm feels, finding that cold and overhydrated skin increases the perception of wetness.

## Contribution

The study reveals that cold-wet stimuli and overhydrated skin heighten wetness perception, offering new insights into thermal and hydration effects on skin sensation.

## Key findings

- Cold-wet stimuli caused higher wetness perception than warm or neutral-wet stimuli.
- Overhydration increased wetness perception only with cold-wet stimuli by 20 mm on the visual scale.
- Dehydration and warm-wet stimuli had less impact on wetness perception compared to overhydration and cold-wet stimuli.

## Abstract

Experiencing wetness on the skin because of sweating or contact with fluids can induce thermal discomfort. Millions of people apply antiperspirant deodorant products to the underarm to minimise this negative experience. However, the mechanisms underpinning wetness perception at the underarm and the influence of underlying stratum corneum hydration remain under investigation. We aimed to evaluate the role of stimulus temperature and skin hydration levels on wetness perception at the underarm in young participants.

Ten healthy participants (5 M/5 F; 29 ± 7 years) underwent a quantitative sensory test during which they reported the perceived magnitude of wetness perception from a short‐duration static application of a cold‐wet (i.e., 5°C below local skin temperature), neutral‐wet (i.e., equal to local skin temperature) and warm‐wet (i.e., 5°C above local skin temperature) stimuli. Wetness perception was assessed on a 100‐mm visual analogue scale (0 = dry; 100 = completely wet), with a repeated measures design exploring the effects of overhydration (+21 %) and dehydration (−40 %) of the underarm's skin.

Our results indicated a higher wetness perception (p = 0.012) during the cold‐wet (40 mm, 95 % CI: 25, 56) than during the warm‐wet (25 mm, 95 % CI: 12, 39), and neutral‐wet stimuli (24 mm, 95 % CI: 7, 40). Furthermore, overhydration of the underarm’ stratum corneum can lead to an increase in wetness perceptions upon contact with cold‐wet stimuli only (mean increase: 20 mm, 95 % CI: 3, 36; p = 0.024; corresponding to 20 % increase).

Our findings provide novel fundamental insights into the underarm's perceptual responses to wetness, which could inform understanding of the determinants of wet feel associated with periods of sweating and the application of antiperspirant products.