Why does head lice cause itchy scalp?

Head lice live close to the scalp and feed by taking small blood meals. Their mouthparts can irritate the skin, while saliva introduced during feeding may prompt an immune response. The scalp may then feel itchy, prickly, or crawling. Some people develop symptoms after the infestation has been present for a while, so the absence of early itching does not exclude lice.

Repeated scratching can cause tiny cuts, scabs, and tenderness. Itchy scalp has many causes, including dandruff, eczema, psoriasis, dry skin, and reactions to hair products. Finding a live louse is more useful than relying on itch intensity alone.

Inspect the scalp under strong light, parting the hair near the ears and the nape. Wet-comb with a fine-toothed comb to help remove lice and nits. If live lice are present, follow one suitable treatment’s instructions carefully, including any required repeat application. Avoid combining products unless a clinician advises it. Clean recently used pillowcases, hats, and brushes, and check close contacts for live lice.

Get advice if the diagnosis is uncertain, the scalp remains itchy after treatment, or live lice are still visible. Arrange prompt medical review for pus, spreading redness, increasing pain, swollen glands, or fever after scratching.

Ask how to distinguish lice from dandruff, which treatment is suitable, how to comb effectively, and what to apply if scratching has broken the skin.