Water immersion skin wrinkling has long been used as a test for sympathetic nerve function. However, the cause of underlying mechanism remained elusive. In this article, we theoretically investigate a possible cause of the phenomenon by taking various properties of sweating into consideration. The pressure exerted by the surface tension of sweat droplets counterbalances the secretory pressure of sweat glands at the pore. When a hand is immersed in water, sweat droplets easily merge with the water, causing the pressure to drop at the pore. Our calculations, using earlier measurements of secretory pressure, show that the water pressure at the sweat pore will be less than the secretory pressure of sweat glands when the hand is immersed at a shallow depth. The resulting pressure imbalance enables the sweat to flow freely into the water. We believe that there will be an initial vasodilation to feed the excess generation of sweat. Sweat flow continues as long as there is blood flow to the hand. To prevent excessive loss of sweat from the body and to maintain homeostasis, sympathetic nerves trigger vasoconstriction to reduce the blood flow to the hand. The overlying skin wrinkles due to loss of volume under the skin. It is possible that denerved fingers remain in the vasodilation state during immersion due to a lack of sympathetic nerve function.

Sweat from the body is regulated by the surface tension of a sweat droplet at the pores and the pressure within the sweat duct. A sweat droplet grows in size until its surface tension and the pressure within the sweat duct are in equilibrium. When a hand is immersed in water, sweat droplets easily merge within the water, causing the pressure to drop at the pores. This in turn makes the sweat to flow freely into the water in the absence of counteracting pressure. Sweat glands produce more sweat because of the low pressure within the duct. To prevent loss of water from the body and to maintain the homeostasis, the body reacts by restricting the blood flow to the hand causing vasoconstriction and eventual wrinkling of the skin.

Water immersion skin wrinkling appears to be a result of breaking the balance between the pressure within sweat duct and the pressure exerted by the surface tension of sweat droplet at the pore. When a hand is immersed in water, sweat droplets easily merge within the water causing pressure to drop at the pores. The resulted imbalance in pressure makes the sweat within the duct to flow freely into the water. To prevent loss of water from the body and to maintain homeostasis, the body reacts by restricting blood flow to hand causing vasoconstriction and eventual wrinkling of skin.

Water immersion skin wrinkling appears to be the result of breaking the balance between secretory pressure of sweat glands and the pressure exerted by the surface tension of sweat droplet at the pore. When a hand is immersed in water, sweat droplet easily merge within the water causing pressure to drop at the pore. The resulted imbalance in pressure enables the sweat to flow freely into the water. Flow of sweat continues as long as there is a blood flow to hand. To prevent the loss of sweat from the body and to maintain homeostasis, sympathetic nerves trigger the reduction of blood flow to hand causing vasoconstriction. The overlying skin wrinkles due to loss of volume under the skin.

Water immersion skin wrinkling has long been used as a test for sympathetic nerve function. However, the cause of underlying mechanism remained elusive. In this article, we theoretically investigate a possible cause of the phenomenon by taking various properties of sweating into consideration. The pressure exerted by the surface tension of sweat droplets counterbalances the secretory pressure of sweat glands at the pore. When a hand is immersed in water, sweat droplets easily merge with the water, causing the pressure to drop at the pore. Our calculations, using earlier measurements of secretory pressure, show that the water pressure at the sweat pore will be less than the secretory pressure of sweat glands when the hand is immersed at a shallow depth. The resulting pressure imbalance enables the sweat to flow freely into the water. We believe that there will be an initial vasodilation to feed the excess generation of sweat. Sweat flow continues as long as there is blood flow to the hand. To prevent excessive loss of sweat from the body and to maintain homeostasis, sympathetic nerves trigger vasoconstriction to reduce the blood flow to the hand. The overlying skin wrinkles due to loss of volume under the skin. It is possible that denerved fingers remain in the vasodilation state during immersion due to a lack of sympathetic nerve function.