The salmon patch, also known as nevus simplex or nevus flammeus simplex, is the most common vascular lesion seen in infants of all races and ethnicities (20%-60% prevalence), usually at birth. The nape of the neck and occiput (also termed "stork bite"), and the lower forehead, glabella, upper eyelids, and sometimes the nose (also called "angel's kiss") are the most common sites. The sacral area, other sites on the scalp or trunk, and limbs are affected less often. There may be multiple lesions. Salmon patches enlarge in proportion to the child's growth. Facial salmon patches generally fade within 1-2 years, whereas those at other sites, especially nuchal, persist into adulthood.

A salmon patch is thought of by some as a type of capillary malformation, and by others as persistence of fetal circulation in the skin.

A variant of the salmon patch known as the butterfly-shaped mark can occur in the sacral region (sacral nevus flammeus simplex). Occult spinal dysraphism has been reported in association with sacral nevus flammeus simplex, although the true prevalence is unknown.