A louse — the name for lice if you're talking about just one of them — is a tiny gray and brown bug that's as big as a sesame seed.
If you get a case of them, they itch like mad. While they're living on your scalp, they eat your blood and lay eggs for more lice.
Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.
© 1995-2016 The Nemours Foundation/KidsHealth. All rights reserved.