Malathion (Ovide) belongs to a class of drugs known as organophosphates. Available by prescription , malathion lotion is FDA approved for the treatment of head lice and works by paralyzing and killing lice and their eggs. Malathion-associated side effects include but are not limited to burning, stinging, dry hair or a temporary increase in dandruff. If you persistently experience any of these effects or they become worse, contact your doctor immediately. Serious allergic reactions to malathion are rare, however rash, itching and swelling – particularly involving the face and throat, or severe dizziness or trouble breathing –have been noted and require immediate medical attention. If you are pregnant or breast feeding, discuss this medication with your doctor before use.