Nevus simplex is a type of capillary malformation. Capillaries are small blood vessels that serve to connect arteries to veins. A capillary malformation (birthmark) is when the small blood vessels are larger than normal. Because the capillaries are close to the surface of the skin, that area appears more pink or red in color.
A nevus simplex, also called a salmon patch, is very common, and is seen in 30–40% of all newborns. Nevus simplex lesions are flat and can occur on any part of the body, but are most commonly seen on the head and neck. Nevus simplex is also frequently called a stork bite or an angel kiss, depending on its location. Most often these fade away or lighten in color in the first year of life.
It is common for this birthmark to become redder when more blood flows to the area, such as when the child is crying, breath-holding, straining with a bowel movement or becoming warm. This temporary change in color does not indicate that the mark is getting larger or reappearing.
A nevus simplex lesion is present when your child is born, and 95% of them will fade away within the first two years of your child’s life without any treatment. For the very rare nevus simplex that does not fade away, a pediatric dermatologist may recommend treatment with a pulsed dye laser to help shrink the vessels’ size and improve the appearance.