Anal fissure: symptoms, causes and how it heals

An anal fissure is a small tear in the lining of your anus that causes pain when you poo. It usually heals on its own, and the first things to try are ones you can do yourself.

Men get anal fissures as often as women: NICE's guidance for GPs says males and females are equally affected. The NHS says they're more common in people aged 15 to 40.

What is an anal fissure?

An anal fissure is a tear or ulcer in the lining of the anal canal (the back passage), just inside the opening of the anus. A fissure is acute if it has been there for less than 6 weeks, and chronic if it has lasted 6 weeks or longer. NICE says fissures are common, although good figures are lacking, and puts the yearly rate at around 1.1 new cases per 1,000 people.

What does an anal fissure look like?

On examination, a fissure may show up as a straight split in the lining of the anus. A new, acute fissure is usually shallow, with well-defined edges. A chronic anal fissure is wider and deeper, its edges are often swollen, and a skin tag may be visible at the end of the fissure. NICE says about 40% of people who see a doctor with an acute fissure go on to have a chronic one.

What are the symptoms of an anal fissure?

The main anal fissure symptoms, according to the NHS, are severe, sharp pain when you poo, burning pain after you poo that may last for several hours, and bright red blood in the toilet or on the toilet paper. NICE adds that some people describe a tearing feeling as the poo passes.

The bleeding is usually a small amount of bright red blood on the poo or the paper. As for what an anal fissure feels like, Cambridge University Hospitals describes the pain as typically sharp and knife-like rather than an ache. It explains that the ring of muscle inside the anus (the internal sphincter) goes into spasm, which makes the pain worse and can stop the fissure healing.

What causes an anal fissure?

It's not always clear what causes an anal fissure. Passing hard poo, or loose poo often, can tear the lining of the anal canal, but NICE says many fissures have no link to constipation or diarrhoea.

One theory in NICE's guidance is that the internal sphincter stays too tight. That reduces the blood flow to the lining, which raises the risk of a tear and slows healing.

The NHS says you may be more likely to get an anal fissure if you:

• have constipation
• have diarrhoea a lot
• have an inflammatory bowel disease (IBD), such as Crohn's disease or ulcerative colitis
• have a sexually transmitted infection (STI), such as syphilis or herpes

NICE adds injury to the anus, for example from previous anal surgery or anal sex, skin conditions such as psoriasis or an itchy bottom (pruritus ani), and some medicines, such as opioid painkillers. A fissure is less common in older adults, NICE says, so a GP should consider other possible diagnoses.

How do you heal an anal fissure at home?

To help an anal fissure heal at home, keep your poo soft with plenty of fluids and fibre, and go when you feel the urge. Ease the pain with paracetamol or ibuprofen and a warm, shallow bath, and keep your bottom clean and dry. That's the NHS's self-care advice, and NICE's guidance for GPs matches it.

1. Keep your poo soft. NICE suggests a balanced diet with wholegrains, fruit and vegetables, adding fibre gradually to avoid wind and bloating, with enough fluid alongside. Cambridge University Hospitals suggests six to ten glasses of water a day.
2. Go when you need to. The NHS says not to ignore the urge to poo, and NICE warns that holding it in or straining hard can make a fissure worse.
3. Have a warm, shallow bath after you poo. The NHS suggests one to ease the pain, and NICE says several a day may help.
4. Use simple painkillers. Paracetamol or ibuprofen can help, says the NHS. NICE advises against opioid painkillers such as codeine, because they can cause constipation and make the symptoms worse.
5. Keep your bottom clean and dry. NICE says this helps healing and avoids infection. See our guide to washing and drying after a poo.
6. Ask a pharmacist if you're constipated. Laxatives help you poo, and you can buy some from pharmacies. The NHS says a pharmacist can help you choose one. It also says to stop bought laxatives once your constipation improves, and to speak to a doctor or pharmacist if they haven't helped after 3 days.

NHS and NICE advice has no shortcut for how to heal a fissure fast, but NICE says keeping these habits up after it heals lowers the chance of it coming back.

How long does an anal fissure take to heal?

NICE's guidance says many acute anal fissures heal within 2 weeks, some without treatment, and around half heal within 6 to 8 weeks of diet changes, lifestyle measures and pain relief. Chronic fissures, lasting 6 weeks or more, often need hospital treatment.

Fissures also come back. NICE says this is common, especially when people stop the diet and lifestyle changes. A Cochrane review of non-surgical treatments (Nelson and colleagues, 2012) found that after GTN ointment, the fissure later came back in around half of the people it had healed.

What are the signs a fissure is healing?

Neither the NHS nor NICE lists signs of healing. The NHS goes by your symptoms: see a GP if they're getting worse, or there's no improvement after 7 days of treating it yourself. Feeling better doesn't always mean the tear has closed, though. NICE's guidance covers fissures still unhealed at 6 to 8 weeks in people whose symptoms have improved a lot; a GP may then continue treatment or refer to a surgeon.

What anal fissure treatment can a GP offer?

If an anal fissure isn't healing, a GP may prescribe glyceryl trinitrate (GTN) ointment; NICE's guidance suggests considering it once symptoms have lasted a week or more without improving. It relaxes the internal sphincter, which lowers the pressure in the anus and improves blood flow to the tear. NICE says there is some evidence that this helps healing.

Anal fissure treatments compared

	What it does.	Who offers it.	Worth knowing.
Self-care	Fibre and fluids keep poo soft; a warm, shallow bath and paracetamol or ibuprofen ease the pain	You, with a pharmacist for laxatives	The NHS says a fissure usually heals on its own
GTN (glyceryl trinitrate) ointment	Relaxes the ring of muscle inside the anus and improves blood flow to the tear	A GP, on prescription	Headache is the most common side effect; not with erection medicines or poppers
Diltiazem ointment	Also relaxes the muscle	A GP with specialist advice, or a hospital team	As effective as GTN in reviews, with fewer headaches; can cause itching
Botulinum toxin (Botox) injection	Relaxes the muscle for about three months while the fissure heals	A hospital specialist, under general anaesthetic	May need repeating; can briefly affect control of wind
Lateral sphincterotomy	A small cut in the muscle stops the spasm so the fissure can heal	A colorectal surgeon; you usually go home the same day	Heals more chronic fissures than any medicine; some risk of changes in control of wind or poo

Sources: the NHS, NICE guidance for GPs, the Association of Coloproctology of Great Britain and Ireland, Cambridge University Hospitals and a Cochrane review. Which option suits you is for you and your GP or surgeon to decide.

The NHS says you may need to use the cream for up to 8 weeks. It also lists laxatives if you're constipated, and medicines to help with pain after you poo, such as mebeverine or hyoscine butylbromide (Buscopan).

The Cochrane review, which included 75 trials and 5,031 people, found GTN healed fissures slightly more often than a dummy treatment (48.9% compared with 35.5%). Headache is its most common side effect and usually stops when treatment does, says NICE. The NHS also lists feeling dizzy and facial flushing, and says alcohol can make you dizzy, faint or sleepy while using GTN.

Tell your GP if you use erection medicines. The NHS says you cannot take medicines for erection problems while you're using GTN, including sildenafil (Viagra), tadalafil (Cialis), avanafil and vardenafil. NICE explains that sildenafil, tadalafil and vardenafil strengthen GTN's effect of lowering blood pressure, and its guidance also rules out combining GTN with amyl or butyl nitrite, the chemicals sold as poppers.

If GTN gives you headaches you can't put up with, NICE says a GP can ask a specialist about diltiazem ointment, an unlicensed product. The reviews NICE cites suggest it is as effective as GTN, with fewer headaches and fewer fissures coming back. The Association of Coloproctology of Great Britain and Ireland (ACPGBI) says its most common side effect is itching around the back passage.

When is surgery needed for an anal fissure?

The NHS says a procedure may be recommended if other treatments haven't worked or you keep getting anal fissures, and gives two examples. It says they're done under general anaesthetic, so you're asleep.

• Botulinum toxin (Botox) injection into the anus, to help the muscles relax so the tear can heal. Cambridge University Hospitals says one injection lasts about three months, during which the fissure should heal, and it can be repeated. It may cause temporary difficulty controlling wind, and possibly liquid poo.
• Lateral sphincterotomy, a small cut in the muscle to reduce tension and let the tear heal. The surgeon cuts part of the internal sphincter, which stops it going into spasm. The ACPGBI says you can usually go home the same day and should feel well enough to go back to work after a few days.

For chronic fissures in adults, sphincterotomy heals more fissures than any medicine: the Cochrane review found no medical treatment came close to it, though none of the medicines in those trials carried its risk to bowel control. The sources describe that risk differently. The ACPGBI says the cut very rarely affects control of your bladder and bowels. Cambridge University Hospitals puts the risk of some change in control of wind or poo at 10% to 20%, and calls sphincterotomy the last resort if the other treatments fail.

Is it an anal fissure or piles?

Both can cause pain and bright red blood when you poo. The NHS lists an anal fissure as a possible cause of bright red blood and pain when pooing, often after constipation, and piles when there is also an itchy bottom or lumps. It says not to diagnose yourself, and to see a GP if you're worried. Our guides to piles in men, what piles look and feel like and how to tell piles from an anal fissure cover the differences.

When should you see a GP about an anal fissure?

See a GP if your anal fissure symptoms are getting worse, or if there's no improvement after 7 days of treating it yourself. Bleeding from the bottom is sometimes a sign of bowel cancer, so the NHS also lists signs that need a GP, an urgent appointment or 999.

See a GP if:

• you've had blood in your poo for 3 weeks
• your poo has been softer, thinner or longer than normal for 3 weeks
• you're in a lot of pain around the bottom
• you have a pain or lump in your tummy
• you've been more tired than usual
• you've lost weight for no reason

Ask for an urgent GP appointment or get help from NHS 111 if:

• your poo is black or dark red
• you have bloody diarrhoea

Go to A&E or call 999 if:

• you're bleeding non-stop
• there's a lot of blood, for example the toilet water turns red or you see large blood clots

If there's a chance of a sexually transmitted infection, a sexual health clinic can test for and treat many STIs. It's free and confidential, and anyone can go, with or without symptoms.

What happens at your GP appointment?

Your GP will ask about your symptoms and look at your anus, the NHS says. NICE advises GPs not to do a finger examination to diagnose a fissure, because it can be very painful. If your GP isn't sure, or the examination causes you pain or painful muscle spasms, you may be referred to a specialist for an examination under general anaesthetic.

If you do have a rectal examination, the NHS says you can ask for a male or female doctor or nurse, and for someone else to be in the room. Try not to be embarrassed: the doctor or nurse will be used to talking about these symptoms.