The anal sphincter is the ring of muscles that open and close the anus. Anal fissures are tears of the lining covering the sphincter. They are common, affecting one in 10 people. Both sexes and people of all ages can get them, but they are found most commonly in children and those aged 15 to 40.
They are commonest in people who are constipated, when a particularly hard or large poo tears the lining of the anal canal. Other causes include persistent diarrhoea, which can irritate the anal lining, inflammatory bowel disease (IBD), such as Crohn’s and ulcerative colitis, or in
