Haemorrhoids develop due to a weakening of the supportive tissue inside the anus.
Certain factors place extra pressure on the blood vessels in the anus, causing haemorrhoids to become enlarged. These include:
- being overweight
- having prolonged constipation or diarrhoea
- being pregnant
- spending long periods of time on the toilet
- regularly lifting heavy objects.
Constipation (having hard bowel motions that are difficult to pass) is an important factor in the development of haemorrhoids because it causes you to strain when you go to the toilet. This puts pressure on the blood vessels in the anus, making them swell.
Haemorrhoids are particularly common during pregnancy. This is because constipation is quite common in pregnancy, but also:
- the growing baby places pressure on the abdomen
- there is more blood flowing through the body
- the hormones produced during pregnancy soften the blood vessels.
Haemorrhoids may also be more common in some families than in others.
Haemorrhoids often go away without any treatment. However, if you notice blood when you have a bowel motion, it is always best to get it checked out by a doctor.
Sources: Colorectal Surgical Society of Australia and New Zealand (Haemorrhoids. Modern management), NHS Choices (UK) (Piles (haemorrhoids), Piles (haemorrhoids) - Causes), Women’s and Children’s Health Network (South Australia) (Pregnancy - Bowel care)
Last reviewed: July 2015