Opinions vary on how effective the use of mayonnaise for lice removal really is. Some say it doesn't work, and others say it works quite well, but only if it’s done correctly. The idea behind the treatment is that mayonnaise suffocates and kills adult lice, which depend on inhaling oxygen through the skin to survive. Killing adult lice then leaves only the task of manually hunting for lice eggs, or nits. Killing adult lice but failing to remove eggs won’t solve the problem, as the infestation will only persist after the eggs hatch.
Medical professionals and individuals in favor of using mayonnaise for removing lice often say that mayonnaise should be left in the hair for a few hours, and that upon rinsing, the hair should be inspected with a nit comb — a special comb made specifically to remove lice eggs from the scalp. To further ensure that the lice are deprived of oxygen, some encourage wearing a shower cap or some other hair cover. Even though there’s no consensus on its effectiveness, many still opt to try out the mayonnaise remedy rather than use chemicals they fear may be harmful to their health.
There are some who, although they believe using mayonnaise for lice removal can work, prefer to use other, less messy smothering agents, such as olive oil. Others simply don’t like the idea of smothering food products in their hair, so they opt for using other nontoxic household items, such as Vaseline®, a petroleum jelly. With other substances, the idea is the same as with mayonnaise: smother and kill the adult lice, and then manually comb out the remaining lice eggs. Some do contend that using mayonnaise for lice actually kills the eggs as well, but the evidence for that is yet more inconclusive.
Others argue that using mayonnaise for lice is not a very effective treatment. It may sporadically kill a few adult lice, but it won’t solve the root of the problem: lice eggs that cause further infestation upon hatching. As a result, some prefer to use professional treatments and dermatological shampoos. Even those treatments, however, typically have to go hand-in-hand with manually picking out lice eggs to ensure complete success. At the end of the day, the only completely proven, foolproof treatment that everyone agrees on is to comb through the hair as many times as necessary to completely pick out all lice and lice eggs.