Derbac-M Liquid

Derbac M Liquid is a treatment for head lice (and their eggs, called nits) that you can buy at a pharmacy without a prescription. It comes in a 150ml bottle and contains an ingredient called malathion that kills the lice on contact. A single application can kill both the live insects and their eggs, but a second application a week later is recommended to be thorough and kill any new lice that might have hatched in the meantime. In addition to head lice, the same liquid can also be used to treat pubic lice ("crabs") and scabies (a skin condition caused by a tiny mite). Because it's water-based and contains no alcohol, it's often a gentler choice for people with asthma, eczema, or sensitive skin

Malathion is a type of chemical called an "organophosphorus insecticide". In simple terms, it works by interfering with how a louse's nervous system works. It blocks an enzyme that the louse needs for its nerves and muscles to function properly. This causes the louse's nervous system to become overactive, leading to paralysis and death

Before you start, check everyone in your household with a fine-toothed detection comb. Anyone with live lice should be treated on the same day so the lice are not passed back and forth.

Apply: make sure the hair is completely dry, then apply enough liquid to cover the whole scalp, from the roots to the tips.

Dry: let the hair dry naturally in a warm room with good airflow.

Leave it on: leave the liquid on for 12 hours before washing it off. Applying it in the evening and leaving it overnight is often easiest.

Rinse and comb: wash the hair with your usual shampoo. While it is still wet, comb through carefully with a fine-toothed nit comb to remove dead lice and eggs.

Second treatment: repeat the whole process 7 days later to kill any lice that have hatched from eggs since the first treatment.

The 150ml bottle is usually enough for two full treatments (one today and one in a week's time) for people with short to shoulder-length hair. You will need a second bottle if you have very long or thick hair and are treating several members of the household at the same time.

The same liquid is used for scabies, but the method is different. Apply it to the whole body from the neck down, including between the fingers and toes and under the nails. Leave it on for 24 hours, then wash it off. If you wash your hands during that time, reapply the liquid to them. Everyone in the household and any close contacts should be treated at the same time, and the treatment is usually repeated after 7 days. Our pharmacy team can advise during your consultation.

Derbac M Liquid is suitable for adults, the elderly, and children aged 6 months and over. Do not use it on babies younger than 6 months unless your doctor says it is safe. You should not use this product more than once a week, and you should not use it for more than three weeks in a row. If you have not got rid of the infestation after three weeks of trying, speak to your doctor or pharmacist for more help.

While Derbac M is generally considered safe, you should always speak to your doctor or pharmacist first for personalised advice before using this medicine if you are pregnant or breastfeeding.

Serious side effects are rare when Derbac-M is used correctly, but some people notice a reaction.

Skin irritation: mild stinging, itching or redness on the scalp or skin where the liquid was applied. If the skin becomes very irritated or starts to burn, wash the product off.

Allergic reaction: the liquid contains preservatives called methyl and propyl hydroxybenzoate, which can sometimes cause an allergic reaction. If you notice swelling of the face, lips, throat or eyes, difficulty breathing or dizziness, stop using the product and get medical help straight away.

No special cleaning is needed. Head lice cannot survive for long away from the scalp, and NHS advice is that you do not need to wash bedding, hats or clothes on a hot wash or use special cleaning products. Washing combs and hairbrushes in hot water after use is a sensible extra step. There is also no need to keep children off school or nursery.

The liquid kills the unhatched eggs inside their shells, but it does not make them magically disappear from the hair. The dead eggs will still be glued to the hair strands. This is why the step of wet combing is so important. You must use a good-quality nit comb to physically remove the dead eggs from the hair after you have washed out the treatment. This stops people from seeing the white specks in the hair and thinking the treatment has failed.

This is an important question. The NHS and experts have noted that head lice in the UK have started to become resistant (immune) to traditional chemical insecticides like malathion. This means that for some families, Derbac M might not work even when they use it perfectly. Because of this resistance, health experts now usually recommend "physical" treatments first. These are products containing dimeticone, which work by suffocating the lice or drying them out physically. The lice cannot become resistant to these physical methods. If you have tried using Derbac M before and it didn't solve the problem, you should try a dimeticone-based product like Hedrin or Full Marks Solution instead.

Yes. Derbac-M Liquid is a pharmacy medicine, so you can buy it from Access Doctor after a short, free online consultation. A 150ml bottle costs £14.99. Our UK pharmacy team reviews your answers to make sure it is suitable before your order is dispatched in discreet packaging.