Full marks preparations contain phenothrin, which is used to treat head and pubic lice infestation. Phenothrin is an insecticide which kills lice by interfering with the insect's biological processes, causing death of the insect and the eggs. Phenothrin solution should be applied to the hair and scalp and left for the recommended length of time, to ensure that all the eggs are treated. This is eventually washed out and the eggs removed from the scalp using a special fine-toothed nit comb. It is usually recommended that family members and close contacts be treated at the same time, if infected. In the event of early re-infestation, phenothrin preparations may be re-applied, provided 7 days have elapsed since the first application. Full Marks is available in a water based (aqueous) solution - Full Marks Liquid or an alcohol based solution - Full Marks Lotion and Mousse. Aqueous solutions are generally preferred in individuals suffering from asthma or eczema and particularly in children, where alcoholic fumes are best avoided.