External hemorrhoids are located underneath the skin that surrounds the anus (lower in the anus than internal hemorrhoids). They can be felt when they swell, and may cause itching, pain, or bleeding with a bowel movement. If an external hemorrhoid prolapses to the outside (usually in the course of passing a stool), you can see and feel it. Blood clots sometimes form within prolapsed external hemorrhoids, which can cause an extremely painful condition called a thrombosis. If an external hemorrhoid becomes thrombosed, it can look rather frightening, turning purple or blue, and could possibly bleed. Despite their appearance, thrombosed hemorrhoids usually are not serious though they can be very painful. They will resolve on their own in a couple of weeks. If the pain is unbearable, your doctor can remove the blood clot from the thrombosed hemorrhoid, which stops the pain.