An itchy scalp and back of the neck, crawling sensations, swollen lymph nodes and pink eye are all indications of a lice infestation, according to the American Academy of Dermatology, but Mayo Clinic notes that some people may not have any symptoms. Seeing live adult lice is a sure sign of an infestation. Seeing their eggs, or nits, may not indicate an active infestation, according to Mayo Clinic.
Some don't experience the swollen glands or itchiness of a lice infestation because their immune systems may not be reacting to the saliva of the insects' bites, states Mayo Clinic. It can take several weeks or even months after a first infestation for symptoms to begin, according to WebMD, but only a few days for symptoms to begin in subsequent infestations. Adult lice are the size of sesame seeds, notes the AAD, but according to Mayo Clinic, they are difficult to spot because they move quickly and avoid light. Nits are easier to see because they are attached to the hair shafts, according to AAD, but they are much smaller. Finding lice and nits requires shining a bright light on the scalp while going through the hair with a fine toothed comb, paying close attention to the nape of the neck and behind the ears where lice and nits are easier to spot, as explained by AAD.