Hemorrhoids develop when pressure on the veins in the pelvic area builds up over months to years, causing veins in the end portion of the large intestine (anal canal) to swell and gradually stretch out of shape.   Persistent pressure also weakens tissues that support the veins in the anal canal. If those tissues become so weak that they can no longer hold the veins in place, the swollen veins and tissues bulge into the anal canal (internal hemorrhoids) or under the skin surrounding the anal opening (external hemorrhoids).For some people, hemorrhoids may cause a little discomfort for a limited period of time. Other people have recurrent bouts of discomfort when hemorrhoids flare up. Some people struggle with hemorrhoid pain, discomfort, and itching much of their lives. During pregnancy, hemorrhoids are common because of extra pressure on the veins of the anus caused by the growing fetus. Hemorrhoids may also develop because constipation is a common problem. During pregnancy, the bowels move more slowly than before pregnancy. In addition, the iron in prenatal vitamins may cause constipation. During labor, hemorrhoids may develop or worsen because of the intense straining and pressure on the anal area while pushing to deliver the baby.The degree of discomfort and how long it lasts depend on where the hemorrhoids develop.


External hemorrhoids may not cause any symptoms. As a result, a person may not be aware that he or she has hemorrhoids. Rarely, a sudden increase in pressure can cause the vein within an external hemorrhoid to break open and bleed. Blood may pool under the skin, forming a hard, bluish lump. This is known as a clotted hemorrhoid.

  • The lump stretches the skin and is extremely painful, especially during the first 24 to 48 hours after it forms. If you see a doctor during this time, he or she may remove the lump, which will probably provide immediate relief from the pain. (See the Other Treatment page in this topic.)
  • If the lump is not removed within 24 to 48 hours, the pain gradually lessens over the next few days. The skin covering the lump may break open on its own, causing mild bleeding from the opening where stool passes out of the body (anus). The pain and bleeding usually stop in about a week. (See the Self-care page in this topic.)
  • After a clot goes away or is drained, the skin covering the hemorrhoid may remain stretched out of shape, forming a skin tag.
  • Sometimes skin tags become swollen and tender. It may be difficult to clean around skin tags. If skin problems such as skin irritation, itching, and burning arise, a doctor may surgically remove the skin tag.


Small internal hemorrhoids may not get larger if bowel habits or other factors change to decrease pressure on the bowel.   Large internal hemorrhoids may bulge from the anus. After bowel movements, a person may have to push these hemorrhoids back through the anus. At worst, large internal hemorrhoids protrude from the anus most of the time.   In rare cases, hemorrhoids may bulge through the anus and swell. Muscles that control the opening and closing of the anus may cut off the blood supply to the swollen hemorrhoids (strangulated hemorrhoid). This may cause the hemorrhoid tissues to die. The person will feel severe rectal pain and may see blood and pus at the anus. He or she will need emergency surgery to prevent further complications, such as death of the affected anal tissue and infection.

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