The difference between lice and dandruff is that lice are contagious parasites, while dandruff is a self-contained scalp condition that causes skin cells on the scalp to shed faster than normal. Lice are spread by direct contact with hair or infested belongings of a person with head lice, while dandruff has a variety of causes, although the most common cause is dry skin.
Although both conditions are indicated by tiny white particles in the hair, close inspection shows that dandruff scales appear as flakes that have a white or yellowish appearance, and they are either dry or oily. On the other hand, lice have three basic appearances, depending on the phase they are in within their life cycle. Eggs, also known as nits, appear as tiny white specks; nymphs appear as small, dull yellow or tan-colored insects; and adult lice are rust-colored insects that are approximately the size of a sesame seed.
Nits are also distinguished from dandruff flakes because they adhere to the hair shaft, while dandruff is easily removed. Head lice are typically found behind the ears and near the neckline of infested people, while dandruff is typically located all over the scalp. Both conditions are diagnosed visually.