Erogenous zones are located all over the human body, but the sensitivity of each varies, and depends on concentrations of nerve endings that can provide pleasurable sensations when stimulated. The touching of another person's erogenous zone is regarded as an act of physical intimacy. Some people may resent stimulation in this manner while others may find it pleasing, and this may also depend on the relationship between the persons involved.
Erogenous zones may be classified by the type of sexual response that they generate. Many people are gently aroused when their eyelids, eyebrows, temples, shoulders, hands, arms and hair are subtly touched. Gently touching or stroking of these zones stimulates a partner during foreplay and increases the arousal level. Also, the gentle massage or stroke of the abdominal area along with kissing or simply touching the navel can be a type of stimulation.
Erogenous zones are either nonspecific or specific.
In these zones, the skin is similar to normal-haired skin and has the normal high density of nerves and hair follicles. These areas include the sides and back of the neck, the inner arms, the axillae (armpits) and sides of the thorax (chest). An exaggerated tickle and anticipatory response are responsible for the heightened sensual response.
Specific zones are associated with sexual response, and include the lips and nipples in addition to areas of the genitals, notably the foreskin and corona of the glans penis, clitoris and rest of the vulva, and perianal skin. The neuroanatomy and neurophysiology of erogenous zones is partly unknown. These zones are apparently mucocutaneous skin. The rete ridges of the epithelium are well-formed and more of the nerves are close to the external surface of the skin than in normal-haired skin. These zones seem to have a high density of innervation, an efficiency of wound healing, and a capacity to stimulate generalized cerebral arousal. Moreover, a connection with the reward system seems also necessary.