Sweat pH

1. Int J Cosmet Sci. 2001 Apr;23(2):99-107. doi: 10.1046/j.1467-2494.2001.00085.x.

Erroneous gender differences in axillary skin surface/sweat pH.

Burry JS(1), Coulson HF, Esser I, Marti V, Melling SJ, Rawlings AV, Roberts G,

Mills AK.

Author information:

(1)Unilever Research, Port Sunlight Laboratory, Quarry Rd East, Bebington,

Wirral, U.K.

Assessing accurately the pH of axillary eccrine sweat is of vital importance in

the antiperspirant industry. Eccrine sweat pH is a critical parameter in

determining the effectiveness of antiperspirants; antiperspirant salts dissolve

in sweat and diffuse into the sweat glands, where the resultant acidic solution

hydrolyses in more alkaline sweat forming an amorphous metal hydroxide gel,

thereby restricting the flow of eccrine sweat. Comparison of the skin surface and

sweat pH of males and females reported in the literature shows that, although

consistent male/female differences have been observed on the forearm,

determination of significant gender-based pH differences across other sites are

less conclusive. Studies on the back and infra-mammary regions exhibited

significant gender differences in skin surface pH, whereas those on the forehead,

cheek, neck and inguinal area showed no such difference. With regard to the

axilla specifically, four studies have been reported, three showing no

significant difference in axillary skin surface pH and one indicating that

females have an eccrine sweat pH of 7 and males have a sweat pH of 5.6. This

paper describes a series of carefully controlled studies aimed at assessing

potential gender differences in eccrine sweat and skin surface pH following

exposure to a variety of temperature, humidity and time conditions. The results

highlight the importance of controlling precisely the time of investigation, site

of measurement and, most importantly, the necessity to pre-equilibrate samples in

40 mmHg carbon dioxide (equivalent to arterial CO(2) tension (pCO2)) before

determining sweat pH. When these parameters are controlled no gender differences

in axillary sweat or skin surface pH are observed. Large differences in eccrine

sweat and skin surface pH are found, however, between the vault (hairy region)

and fossa (non-hairy region) of the axilla.

PMID: 18498454  [PubMed]