What should you know about head lice side effects?

The infestation commonly triggers an itchy scalp, small red bumps, and soreness from scratching. Broken skin can become infected, causing increasing pain, warmth, pus, or crusting. A treatment can also cause temporary stinging, dryness, redness, or irritation, especially when used too often or left on too long. Persistent itch alone does not prove that live lice remain, so inspect the hair and scalp before repeating a product.

Use only the amount and contact time stated on the label. Rinse thoroughly, avoid applying a product to broken or inflamed skin unless a clinician says it is appropriate, and keep it out of the eyes. Do not scratch; a cool compress and gentle cleansing may soothe irritation. Stop using a product that causes marked burning or a spreading rash and ask a pharmacist or doctor what to use next.

Seek prompt care for facial swelling, breathing difficulty, blistering, severe burning, or a rapidly spreading rash after treatment. Arrange a GP Consultation for pus, fever, worsening scalp pain, or sores that do not settle. A clinician can distinguish treatment irritation from an infection or another scalp condition.

Ask whether the reaction fits the product used, whether another treatment is suitable, and how to manage itching without damaging the scalp.