Treatment is likely to be more thorough if someone else in the household applies it. This may be unpleasant or inconvenient for the person applying the medication. The chemicals have unpleasant smells and may cause reactions in some people. Medical advice is therefore needed before using them in very young or asthmatic children. Some anecdotal evidence suggests that other methods may work on head lice.
Head lice are unpleasant but can be treated relatively easily.