About Malathion Organophosphate compound Mechanism of Action of Malathion Malathion works by blocking the action of an enzyme in the parasite called cholinesterase. This enzyme is essential for the growth and survival of the parasite. By inactivating it, malathion disrupts vital metabolic processes in the parasites and ultimately leads to their death. Indications for Malathion For the eradication of head lice infestation.