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How to treat pinworms and perianal strep

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When it comes to itchy bottoms, a bath might be the quick fix. Diapers, sweat and dirt can all cause irritation (not to mention playdates in the sandbox). Sometimes creams and soaps can aggravate the skin and be the problem. Occasionally, the itch does not resolve and it’s something more. Two of the most common causes of an itchy bum are pinworm and perianal strep. Don’t panic; these two entities are very common and are not caused by poor hygiene.


Some children with pinworm don’t have symptoms, but most do get itchy around the anus (and vagina in girls) especially at nighttime. Infected children are restless during sleep and will scratch their bum during the night. This is because the pinworms live in the rectum and at night the adult worm crawls out of the anus and lays eggs on nearby skin. When a child scratches the bum, eggs get under the fingernails and then are ingested when hands get put in the mouth. Infected fingernails can also leave eggs on toys and other areas where indirect transmission can occur. The eggs can be very persistent, living for up to two weeks outside the body on clothing, toys, objects and bedding before being ingested by another child.

Pinworms do not cause health problems, tummy pain or weight loss. They are more of a nuisance and irritation. Pinworms are tiny (1 cm long), wiggly, white and thread-like sized. You may or may not see them. We used to ask parents to go looking for pinworms at night or use tape to collect eggs over the anus, but this is not necessary and can cause undue distress to the parent/caregiver and child and is not always successful. If you don’t see anything it doesn’t mean your child doesn’t have pinworms (similar to going fishing – just because you don’t catch any fish doesn’t mean there aren’t fish in the sea).

Pediatricians recommend treating your child if they have symptoms. There is over the counter (OTC) medication you can get without seeing a doctor, which is very safe and effective. Because 30 percent of children get pinworm, medication is readily available to treat your child quickly. If you see a doctor, they will recommend the same OTC medication or they may give you a prescription. Your child takes the medicine and then repeats the same dose in two weeks due to the life cycle of the worms. It is recommended that other young children get treated, but adults don’t need to take the medication unless they are symptomatic.

You can reduce transmission by washing your child’s hands thoroughly after using the toilet and keeping fingernails clean and short. Discourage thumb sucking and nail biting.

Perianal Strep

A second cause of an itchy bum is perianal strep (streptococcus). Yes, this is the same kind of bacteria that causes a strep throat, but this time the bacteria infects the other end of the gi (gastrointestinal system). Children may swallow the bacteria, which then descends to the anal area or they may digitally contaminate themselves from an infected throat or other sites of strep infections (eg. impetigo around the mouth). In addition to itchiness, children may complain of rectal pain and occasional blood-streaked stools can be seen. When examined, the anus is bright red in colour with a rash that can extend up to 3 cm circumferentially around the perianal area. If left untreated the rash can spread to the vulva or onto the scrotum and anal fissures can develop causing the blood seen alongside the stools.

A rapid strep test around the anus using a swab can be done in your doctor’s office (similar to checking strep in the throat). If positive, then a 10-day course of oral antibiotic therapy will clear the infection. Topical preparations are not effective.

Janine Flanagan is a pediatrician at St. Joseph’s Health Centre and The Hospital for Sick Children in Toronto.

Originally published in ParentsCanada magazine, Summer 2017.

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