A birthmark is an area of discolored and/or raised skin that is present at birth or appears within a few weeks to a few years of birth. Some birthmarks such as a Becker’s nevus appear during the teenage years for the first time. Birthmarks can be caused by various factors, but the exact cause of most types of birthmarks is unknown. However, some birthmarks are hereditary and run in families, while others are caused by gene mutations. There are different types of birthmarks, and each has its own specific cause. For example, red birthmarks are caused by an overgrowth of blood vessels. The most common type of red birthmarks are hemangioma, which are usually harmless and painless. Hemangiomas are a bright red birthmark that appears at or soon after birth and is made up of extra blood vessels in the skin. Another type of birthmark is the port-wine stain, which is caused by the malformation of blood vessels in the skin. This birthmark can vary in size and shape and typically appears on the face, neck, or upper trunk. It is often present at birth and may darken over time. There are many types of other birthmarks that are brown in color. These include cafe au let macules, Becker’s nevi, melanocytic nevi, congenital melanocytic nevi or hairy nev, nevus of ota or ito, nevus spilus and others. These are brown gray or black and are caused by either an increased production of melanin or increased number of melanocytes. These as a category are referred to as pigmented birthmarks. Overall, while the exact cause of most birthmarks is unknown, they are typically benign (noncancerous) and do not require treatment. However, if a birthmark changes in size, shape, or color, or causes other symptoms, it is important to consult a doctor to rule out any potential health concerns. Other birthmarks can be a sign of systemic disease or underlying syndromes and should be investigated through seeing a board certified dermatologist. Many people are bothered by the appearance of certain birthmarks in cosmetically sensitive areas. There are birthmarks that can cause functional issues. For example, birthmarks around the eyes can block visions or cause field of vision issues.