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Threadworm, mebendazole and breastfeeding

It has been suggested that up to 40% of children get threadworms at some stage. The whole family needs to be treated, even the breastfeeding mother. The joys of being a mum!

Factsheet pdf available here:


Symptoms of threadworms

Threadworms are very common in toddlers and primary school age children who can sadly infect the rest of the family. They are not a sign of poor hygiene. The exact prevalence is not known but it has been estimated that up to 40% of children in the UK will have threadworm infestation at some time in their lives. The symptoms are:

  • Intense itching around the anus, typically worse during the night.
  • Some people may not experience itching but  small white thread-like worms (which may be slowly moving) are seen on the perianal skin or in the stools.
  • In females, there may be itching around the vulva/vagina.
  • Night-time itching may lead to disturbed sleep and irritability.


Everyone in the household needs to be treated with mebendazole ( available over the counter as Ovex™ or on prescription as Vermox™. Mebendazole can be given at a dose of 100mg to everyone over the age of 6 months. Mebendazole kills the worms but not the eggs which can survive for up to 2 weeks. If reinfection occurs, second dose may be needed after 2 weeks.

Prevention of re-infection


  • wash hands and scrub under fingernails – particularly before eating, after using the toilet or changing nappies
  • encourage children to wash hands regularly particularly under nails
  • bathe or shower every morning
  • rinse toothbrushes before using them
  • keep fingernails short
  • wash sleepwear, sheets, towels and soft toys (at a hot temperature)
  • disinfect kitchen and bathroom surfaces (particularly the area behind the toilet as eggs may spread if the child scratches
  • vacuum and dust with a damp cloth
  • make sure children wear underwear at night – change it in the morning
  • change toys such as Playdough which can get behind fingernails and become infected with eggs if the child has scratched and not washed hands

Eggs can pass to other people when they touch contaminated surfaces and then touch their mouth. They take around 2 weeks to hatch.

Threadworms in pregnancy


Babies under 6 months

Treat with hygiene measures only and watch for signs when changing nappies

Treating Babies 6 months to 2 years

Unlicensed so may need to be prescribed https://bnf.nice.org.uk/drugs/mebendazole/

Threadworms when breastfeeding

Oral bio availability poor 2-10%, Highly plasma protein bound, Relative Infant Dose 0.06%.

It is unlikely that mebendazole is  transmitted to the infant in clinically relevant concentrations and breastfeeding can continue as normal even if the nursling is also receiving a dose.

Other sources of information

A-Z NHS Conditions


Elactancia https://www.e-lactancia.org/breastfeeding/mebendazole/product/

BNF Mebendazole  https://bnf.nice.org.uk/drugs/mebendazole/ “Amount present in milk too small to be harmful but manufacturer advises avoid”

McCormick, A., Fleming, D. and Charlton, J. (1995) Morbidity statistics from general practice. Fourth national study 1991-1992. Office of Population Censuses and Surveys. http://www.statistics.gov.uk

CKS Threadworm https://cks.nice.org.uk/topics/threadworm/

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