Acidic secretions from skin glands also retard the growth of fungi. Heat and cold receptors are located in the skin. The hypothalamus also causes dilation of the blood vessels of the skin, allowing more blood to flow into those areas, causing heat to be convected away from the skin surface. When body temperature falls, the sweat glands constrict and sweat production decreases. If the body temperature continues to fall, the body will engage in thermiogenesis , or heat generation, by raising the body's metabolic rate and by shivering.
Water loss occurs in the skin by two routes.
Skin damaged by burns is less effective at preventing fluid loss, often resulting in a possibly life threatening problem if not treated. Deeper within the skin are Meissner's corpuscles , which are especially common in the tips of the fingers and lips, and are very sensitive to touch. Pacinian corpuscles respond to pressure. The skin also assists in the synthesis of vitamin D. Children lacking sufficient vitamin D develop bone abnormalities known as rickets. The skin is selectively soluble to fat-soluble substances such as vitamins A, D, E, and K, as well as steroid hormones such as estrogen .