Threadworms Treatment in Breastfeeding Mothers

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The information provided is taken from various reference sources.  It is provided as a guideline.  No responsibility can be taken by the author or the Breastfeeding Network for the way in which the information is used.  Clinical decisions remain the responsibility of medical and breastfeeding practitioners.  The data presented here is intended to provide some immediate information but cannot replace input from professionals.

Threadworms are small, white, thread-like worms between 2 and 13 mm long.  Infection in children is common and toddlers may infect their mothers who may be breastfeeding.  Threadworms live for about 6 weeks in the gut, and then die.  The female worms lay tiny eggs around the anus and these cause intense itching.  Transfer of the ova back into the mouth perpetuates the infection.  Careful washing of hands and scrubbing beneath the nails, which should ideally be kept short, is essential.  Tight fitting underwear for children prevents scratching in the sleep.  Threadworm eggs can also survive for up to two weeks outside the body and so can be moved from sheets into the general household environment.  Infection is not serious but is unacceptable to most families.  If left untreated, but with strict hygiene measure to ensure no further eggs are swallowed, the worms will die out in 6 weeks.

For further information see

Medication to treat threadworm infections is generally used in addition to hygiene measures.

Mebendazole (Vermox®, Ovex®, Pripsen tablets®).

Adults and children over the age of two take 100milligrammes (one tablet) with a second dose after 2 weeks if re-infection is suspected.  It may be given to children under the age of 2 years but is not licensed for such use (BNFC).  The BNF states that the amount excreted into breastmilk is too small to be harmful although the manufacturer advises avoidance under the limitations of licensing.  For explanation see

Mebendazole is poorly absorbed from the gastro intestinal tract.  It undergoes extensive first pass metabolism and is highly protein bound, so only low levels are likely to reach breastmilk (Jones 2018, Martindale 2007).  Side effects in the mother are generally gastro-intestinal with tummy cramps and diarrhoea reported (BNF).  Preparations are not licensed during lactation but as it is virtually unabsorbed from the gut it is unlikely to cause adverse effects in the baby or to affect breastmilk supply.

Piperazine (Pripsen®)

Piperazine is reported to be excreted in breast milk (Leach 1990) but no reports on the amounts have located.  According to the manufacturer, the mother should take her dose of the drug immediately following feeding her infant, and then express and discard her milk during the next 8 hours (BNF, Leach 1990).  It is readily absorbed from the gastro intestinal tract.  It is given directly to babies down to 3 months of age (BNFC) suggesting that the amount reaching a breastfed baby is safe (Jones 2018).  However use of mebendazole is preferable based on available safety data (Jones 2018, LactMed).


  • British National Formulary
  • British National Formulary for Children
  • Jones W Breastfeeding and Medication 2018 Routledge
  • LactMed
  • Leach FN. Management of threadworm infestation during pregnancy. Arch Dis, Child 1990;65:399400.
  • Martindale the Extra Pharmacopeia 2007

©Dr Wendy Jones MBE, MRPharmS and the Breastfeeding Network Sept 2019