Temperature - Through its extensive blood supply and sweat glands, the mammalian skin is able to maintain the constant temperature of a homoiotherm. The skin is our primary source. Through the extensive network of sensory receptors we have sensations of pressure, texture, temperature and pain. Pigmentation - Melanin pigments protect against the excesses of ultra violet light. It prevents absorption of unwanted and potentially dangerous chemicals.
Skin performs an active role in immunity through immunological surveillance.
In short, the skin acts as a barrier and is the primary organ through which we interact with the external world. Significant in many of these properties is the hair follicle appendage. The key role of hair is to provide protection against heat loss. Hair traps air adjacent to the skin to provide an invisible, insulating layer. Several mammalian species produce special dense winter coats with added heat trapping properties.