Malathion (for head lice)

Date: February 2018, Version 2.0

Quick read

Head lice can be treated in pregnancy using wet combing with conditioner and a fine-tooth comb, or using an insecticide treatment that kills the lice. 

What are head lice?

Head lice are tiny insects that live in head hair and cause itching. Nits are the eggs that are sometimes visible in the hair. 

Head lice are easily spread and are common in children. You can look for head lice by combing hair with a special fine-toothed comb that traps the lice. If one member of your household has head lice, you should check everyone else in the house and treat all affected individuals at the same time.

How do I treat head lice during pregnancy?

Wet combing

Current UK guidelines recommend that pregnant women who need to treat their own or their child’s head lice can use ‘wet combing’. This avoids the use of any chemicals. Wet combing involves thorough, frequent combing of wet hair with a special comb and conditioner. Further information on wet combing can be found on the NHS A-Z leaflet Head lice and nits


If wet combing is not effective or is not preferred, insecticides (products that kill insects) can be used. 
There are two types of insecticides: 
1.    Physical insecticides which coat the head lice and kill them by blocking their breathing and/or water balance. 
2.    Chemical insecticides which kill head lice by poisoning them.

Physical insecticides 

Dimethicone (Hedrin® products, Lyclear® Spray, Linicin® Lotion, NYDA® Spray), cyclomethicone (Full Marks® Solution), and isopropyl myristate and isopropyl alcohol (Vamousse®) kill head lice by blocking their breathing and/or water balance. Physical insecticides are harmless to humans and also do not enter the bloodstream in amounts that could cause problems for the baby.

Chemical insecticides

Malathion (Derbac® M Liquid, Prioderm® Lotion) is a chemical insecticide that kills head lice by poisoning them. 

No studies have been carried out to look at whether using malathion to treat head lice during pregnancy affects the baby. However, if malathion is used as recommended by the manufacturer, any risk is expected to be very low as it will only enter the bloodstream in tiny amounts. As a precaution, it is recommended to first try the other methods to clear head lice in pregnancy and only use malathion if these have not worked. 

Will my baby need extra monitoring during pregnancy?

As part of their routine antenatal care, most women will be offered a scan at around 20 weeks of pregnancy to look for birth defects and to check the baby’s growth. 

Using treatments for head lice during pregnancy is not expected to cause any problems that would require extra monitoring of the baby.  

Are there any risks to my baby if the father has used head lice treatments?

There is currently no evidence that head lice treatments used by the father can harm the baby through effects on the sperm. 

Who can I talk to if I have questions?

If you have any questions regarding the information in this leaflet please discuss them with your healthcare provider. They can access more detailed medical and scientific information from

How can I help to improve drug safety information for pregnant women in the future?

Our online reporting system (MyBump Portal) allows women who are currently pregnant to create a secure record of their pregnancy, collected through a series of questionnaires. You will be asked to enter information about your health, whether or not you take any medicines, your pregnancy outcome and your child's development. You can update your details at any time during pregnancy or afterwards. This information will help us better understand how medicines affect the health of pregnant women and their babies. Please visit the MyBump Portal to register.

General information
Sadly, miscarriage and birth defects can occur in any pregnancy.

Miscarriage occurs in about 1 in every 5 pregnancies, and 1 in every 40 babies are born with a birth defect. This is called the ‘background risk’ and happens whether medication is taken or not.

Most medicines cross the placenta and reach the baby. For many medications this is not a problem. However, some medicines can affect a baby’s growth and development.

If you take regular medication and are planning to conceive, you should discuss whether your medicine is safe to continue with your doctor/health care team before becoming pregnant. If you have an unplanned pregnancy while taking a medicine, you should tell your doctor as soon as possible.

If a new medicine is suggested for you during pregnancy, please make sure that the person prescribing it knows that you are pregnant. If you have any concerns about a medicine, you can check with your doctor, midwife or pharmacist.

Our Bumps information leaflets provide information about the effects of medicines in pregnancy so that you can decide, together with your healthcare provider, what is best for you and your baby.