Hemangiomas are benign tumors that develop due to rapid growth of the endothelial cells that line blood vessels. The tumors usually appear within the first few weeks of life. In most cases, superficial hemangiomas resolve independently by the time the child is ten years old. However, while a hemangioma is present, the risk for certain complications is increased and some of these are described below.

• Some superficial hemangiomas may break down on the surface and become ulcerated. Ulceration that is deep can sometimes cause a significant amount of bleeding. Ulceration is most likely when the hemangiomas occur around the mouth, in the nappy area or in skinfolds such as the neck or armpit. The ulceration is caused by two skin surfaces in these areas rubbing together.
• Hemangiomas may also occur in the larynx, which can disrupt breathing.
• Although hemangiomas can appear on any part of the body, they usually appear in the head or neck area, particularly on the eyelid, upper lip and cheeks. If a hemangioma grows large enough to block the eye, the occlusion is referred to as amblyopia.
• If a hemangioma becomes very large, it can require large amounts of blood to supply its vessels, which can cause high-output heart failure if the heart pumps hard enough.
• Hemangiomas that grow alongside bones can erode the bone.
• Hemangiomas that grow on the lip or nose can cause psychological distress and the most frequent complaints about hemangiomas involve the psychosocial aspect of living with the tumors when they attract unwanted attention.