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Date of issue: August 2023, Version: 3

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A corresponding patient information leaflet on USE OF HEAD LICE TREATMENTS IN PREGNANCY is available.

Head lice (Pediculus humanus capitis) are parasitic insects that infest the hairs of the human head and feed on blood from the scalp. Head lice can be eradicated by ‘wet combing’ the lice and eggs from the hair with a fine-toothed comb and conditioner, using dimeticone-based treatments, or malathion, a chemical insecticide.

Exposure to topical head lice treatments would not be expected to cause fetal harm as they will not enter the maternal bloodstream in appreciable amounts.

The most commonly used topical head lice treatments are based on dimeticone (derived from silicone), an inert chemical widely found in antacid medications and cosmetics. There are no human pregnancy exposure data but adverse effects are not anticipated.

Malathion-based insecticide treatments for head lice are also available. There are two case reports of pregnancy outcomes following topical malathion use in pregnancy, with one malformed infant and one uneventful outcome described. Resistance to malathion has also been noted and it may be preferable, at least initially, to use other means to treat head lice during pregnancy.

Exposure to head lice treatments at any stage in pregnancy would not usually be regarded as medical grounds for termination of pregnancy or any additional fetal monitoring. However, other risk factors may be present in individual cases which may independently increase the risk of adverse pregnancy outcome. Clinicians are reminded of the importance of consideration of such factors when performing case-specific risk assessments.

This is a summary of the full UKTIS monograph for health care professionals and should not be used in isolation. The full UKTIS monograph and access to any hyperlinked related documents is available to NHS health care professionals who are logged in.

If you have a patient with exposure to a drug or chemical and require assistance in making a patient-specific risk assessment, please telephone UKTIS on 0344 892 0909 to discuss the case with a teratology specialist.

If you would like to report a pregnancy to UKTIS please click here to download our pregnancy reporting form. Please encourage all women to complete an online reporting form.

Disclaimer: Every effort has been made to ensure that this monograph was accurate and up-to-date at the time of writing, however it cannot cover every eventuality and the information providers cannot be held responsible for any adverse outcomes of the measures recommended. The final decision regarding which treatment is used for an individual patient remains the clinical responsibility of the prescriber. This material may be freely reproduced for education and not for profit purposes within the UK National Health Service, however no linking to this website or reproduction by or for commercial organisations is permitted without the express written permission of this service. This document is regularly reviewed and updated. Only use UKTIS monographs downloaded directly from to ensure you are using the most up-to-date version.