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 special fine-toothed detection comb to see if they have any live lice. Anyone who does should be treated on the same day to stop the infestation from spreading around the family again. For head lice, the process is: Apply: Make sure the hair is completely dry. Apply enough liquid to the hair to cover the whole scalp, right from the roots to the tips. Dry: Let the hair dry naturally in a room that is warm but has good airflow. Do not use a hairdryer. If you are using a hairdryer, take care because the product is flammable while it is still wet. Leave it on: You must leave the liquid on the hair for at least 12 hours before washing it off. The best way to do this is to apply it in the evening and leave it on overnight. Rinse and comb: After 12 hours, wash the hair as usual with your normal shampoo. While the hair is still wet, comb through it carefully with a fine-toothed nit comb to remove the dead lice and eggs. Second treatment: This is very important. Repeat the whole treatment again 7 days after the first application. This kills any lice that may have hatched from eggs that survived 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.

You use the same Derbac M liquid for treating scabies, but the method is different. You apply it to your whole body (not just the head). Leave it on for 24 hours (not 12). After that time, you can wash it off in a normal bath or shower.

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 very rare when you use the product correctly, but some people might notice a mild reaction. Skin irritation: Some people may experience mild stinging, burning, itching, or redness on the scalp or skin where the liquid was applied. 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, or throat, or have difficulty breathing, stop using the product immediately and get medical help. Fire risk: The liquid is flammable while it is still wet on the hair. Keep away from open flames, gas stoves, cigarettes, and other sources of ignition (including hair dryers) until the hair has been washed and dried.

Head lice can only live for a very short time away from the human scalp – usually less than 48 hours. So you do not need to do any heavy chemical cleaning. Just wash your child's bedding, hats, and recently worn clothes at 60°C (the high temperature kills the lice) and put hairbrushes and combs in boiling water for 5 to 10 minutes. You should also vacuum the sofa, car seats, and any carpeted areas where someone with an infestation may have rested their head to pick up any stray hairs that could still have lice eggs attached.

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.