Malathion is available in a 0.5% preparation or a 1% shampoo for head lice. Malathion lotion, which is available in the United States as Ovide, was removed from the market in Canada by the company in 1991 because more effective compounds were available.


  1. Apply lotion on dry hair using enought to thoroughly wet the hair and scalp, and allow the hair to dry naturally.
  2. Shampoo the hair after 8 to 12 hours or as directed by your physician, and use a fine-toothed comb to remove dead lice and eggs.
  3. If live lice are found seven to ten days after treatment, repeat treatment.


Malathion contains alcohol, and it may cause stinging. The effectiveness of the malathion preparations as ovicidal agents is very dependent upon the excipient (vehicle) in the product. The original preparation of Prioderm, introduced in the late 1970s into the United Kingdom, contained terpene and was quite effective. Later formulations did not contain terpene with the malathion and killed only 35% to 37% of the eggs. The malathion preparation Ovide currently available in the United States does contain terpineol, limonene and pine needle oil. It is safe to use while pregnant or if you are breastfeeding.