Water UK

Water and the skin

The skin acts as a water reservoir and participates in the fluid regulation of the whole body. The skin tissue volume of a 70kg man is about 7 litres. Approximately two thirds of this volume exists outside the skin cells. The other third of the tissue layer consists of interchangeable water which is stored mainly in the dermis. Different layers of the skin vary in their water content, for example the epidermis is approximately 80% water, whereas the dryer surface of the skin, the stratum corneum, is made up of dead skin cells and has a water content varying between 10% and 30%.

Skin thickness depends on the amount of collagen fibres, cellular substances and interstitial fluid content. The fluid content of the skin determines its biophysical properties such as turgor, elasticity and distensibility. Increasing the fluid content of the skin leads to a greater skin thickness.(1)

Effects of dehydration

Studies in animals have shown that there is a direct relationship between total body water and the water content of the skin.(2) For example, dehydration can reduce the water content of the skin from 70.6 to 65.85%. The water content is partially restored one hour after rehydration.(3) In humans, slight changes in the water distribution of the body, eg due to water retention or dehydration, influence the thickness and echodensity of the dermis, eg skin thickness increased after fluid infusion and decreased after dehydration. These changes can be more pronounced at the forehead than on the lower legs.(1)

It is not surprising, therefore, that dehydration is associated with changes in the appearance of the skin. In mild dehydration the skin may appear flushed, dry and loose, with a loss of elasticity.(4,5) (Loss of elasticity may be demonstrated by pinching the skin on the back of the hand and observing the time taken for the skin to return to its normal position. Recovery will be slower if the body is dehydrated.) However, loss of skin elasticity is also associated with ageing,(1,6) and hence, dehydrated skin may appear to be older than it actually is.

Dehydration at a level of 4% loss of body weight due to fluid loss, does not appear to alter, skin temperature, and cold-induced vasodilation during exposure to the cold. A decrease in plasma volume may affect peripheral blood flow during cold exposure, but this does not seem to increase people’s susceptibility to peripheral cold injury,such as ‘frostbite’.(7)

Last updated: December 2006

(1) Eisenbeiss C, Welzel J, Eichler W and Klotz K. Influence of body water distribution on skin thickness: measurements using high-frequency ultrasound. Brit J Dermatol 2001;144:947-951
(2) Campbell SE, Ostrowski R,Hoarau C, Durr N,Debreczeny MP. A novel method to determine lean body water using localized skin biopsies: correlation between lean skin water and lean body water in an overhydration model. Am J Physiol Regul Integr Comp Physiol 2006;291:R1539-R1544
(3) W Bianca. Effects of water deprivation on the water content of cattle skin. Int J Biometeorol 1968;12:153-157
(4) Principles of Human Nutrition. Ed M Eastwood. Chapter 8: Water, electrolytes, minerals and trace elements. London: Chapman & Hall 1997
(5) Kleiner SM. Water: An essential but overlooked nutrient. J Am Diet Assoc 1999;99;201-7
(6) Katayama S. Aging mechanism associated with a function of biowater. Physiol Chem Phys 1992;24:43-50
(7) O'Brien C and J Scott. Montain Hypohydration effect on finger skin temperature and blood flow during cold-water finger immersion. J Appl Physiol 2003;94:598-603