Physical Insecticides

These products contain chemicals that coat the outside of the lice and suffocates them. Lice are less likely to become resistant to these. They usually contain dimeticone, isopropyl myristrate or isopropyl alcohol. A 2016 study (Kolber The louse is (no longer) in the house - PMC) found dimeticone to be the most effective of these.

There are a range of different preparations of these ranging from lotions to sprays, gels and mousses.

The products should be applied to all areas of the scalp and all of the hair (from root to tip). The product should be left on for the manufacturer’s recommended time and then washed off. It is generally recommended that these products are applied twice at least 7 days apart although some experts suggest a third application is necessary.

After treatment, detection combing should be done to check if the treatment has been successful.

Advantages:

• Dimeticone has a well-established safety profile and is usually well tolerated

• High cure rates have been reported where clinical trials have been carried out

Disadvantages

• A lot of physical insecticide preparations lack safety data on use by pregnant and breastfeeding patients – dimeticone 4% lotion is the recommended first line treatment for these patients as it is suggested that there is no data to prevent its use in pregnancy

• Minor side effects such as skin irritation have been reported with dimeticone