Many people only experience a little itching discover the crab lice by accident. For other, itching, especially in the crotch, is an outstanding symptom of crab lice. Itching in the groin area can have many other causes (among the animals, the flagellate Trichomonas vaginalis or pin worm Oxyuris vermicularis, may cause itching. These two kinds of animals are not affected by crab louse treatment).

The easiest way of detecting lice in beards, armpit hairs, chest hairs and pubic hair is to comb the hair with a fine-tooth comb. The comb will pull out the hairs which put up resistance and it is usually hairs with nits on them.