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Lice are clear and become darker when they feed. Nits, the lice eggs, are about the size of a sesame seed.

The most common sign of a head lice infestation is an itchy scalp. The saliva of the louse is left on the scalp in tiny lesions after a blood meal. This saliva is what causes irritation and can lead to intense itching.

Close inspection of the scalp can identify other indications of head lice infestation:

  • Look for nits (lice eggs), nit shells, live lice and small dark fragments of the louse feces.
  • Nits can be confused with dandruff, dry scalp or hair spray. If they separate easily from the hair strand, they are not nits. Nits will remain firmly attached.

If head lice are left untreated, the infested person may be at risk for a secondary infection due to the scratching of the scalp with unclean hands. Very severe cases may cause swollen lymph glands.