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.