Why does anal fissure cause blood in stool?

Hard or large stool can stretch the area and disrupt healing, causing fresh blood that is often noticed on wiping. Blood in Stool is a very common presentation of Anal Fissure, although rectal bleeding can also come from other conditions.

The anal lining is sensitive and has a rich blood supply. When it tears, passing stool across the wound can cause sharp or burning pain and a small amount of visible blood. Muscles around the anus may tighten in response to pain, which can reduce blood flow to the tear and make healing slower.

Constipation is a frequent trigger, but loose stool and repeated diarrhoea can also irritate the area. A clinician can examine the area and check whether a fissure explains the symptoms.

Keep stools soft by drinking fluids, eating fibre-containing foods if appropriate for you, and following advice from a clinician or pharmacist. Avoid straining or delaying the urge to pass stool. Warm water soaks may ease discomfort; use only creams or laxatives recommended for your situation, particularly during pregnancy or while taking other medicines.

Seek urgent medical help for heavy bleeding, black or tar-like stool, fainting, severe weakness, fever, or escalating pain with swelling. Book a medical assessment for bleeding that persists, returns often, or is accompanied by a new bowel change, weight loss, or abdominal pain.

Ask whether the tear appears acute or longstanding, how to soften stool safely, and when follow-up is needed. Mention any bowel disease, recent childbirth, medicines, or recurrent symptoms that could influence treatment.