The school nurse is screening the kindergarten students. She notices many of the children are scratching their heads. Which is a common sign of head lice?

A. White flakes that are easily removed from hair shaft: This description is characteristic of seborrheic dermatitis or dandruff rather than Pediculosis humanus capitis. Lice nits are firmly cemented to the hair shaft by a chitinous substance and cannot be flicked or blown away. Ease of removal is a primary clinical differentiator from an active infestation. B. Patchy bald spots over the scalp: Alopecia areata or tinea capitis typically cause localized hair loss and circular bald patches. While scratching from lice can cause secondary excoriation, it does not typically result in discrete areas of hair loss. Bald spots suggest a fungal infection or an autoimmune process rather than parasites. C. Light brown colored dots attached to hair at nape of neck: These represent nits, which are the eggs of head lice, frequently found in warm areas like the nape of the neck or behind ears. Their firm attachment to the hair shaft and proximity to the scalp are definitive diagnostic markers. Identifying these is the standard for confirming a lice infestation. D. Thick yellow crusts on the scalp: This finding is most often associated with "cradle cap" or severe seborrheic dermatitis, which involves an overproduction of sebum. It is an inflammatory skin condition rather than a parasitic infestation. While it may cause itching, it lacks the specific presence of nits or live lice.