Living lice and eggs were found in 19% of 2643 children examined in Israel. Boys and girls were equally infested. Bite reactions, pruritus, excoriations, lymphadenopathy, and conjunctivitis were the most common signs and symptoms. Bite reactions, pruritus, excoriations, and conjunctivitis were found more frequently in infested children than in noninfested children. Lymphadenopathy, eczema, influenza, herpes, crusts behind ears, blepharitis, seborrhea, psoriasis, erythema, vitiligo, secondary infections, and scars were equally common in both groups. The sequence of the skin reactions of a volunteer to continuous exposure to lice bites was as follow: phase I, no clinical symptoms; phase II, papules accompanied by pruritus of medium intensity; phase III, wheal formation immediately after the bite, followed by a delayed papular reaction and intense itching; phase IV, papular reaction with diminished reactivity of the skin and mild pruritus. Healed bite reactions reappeared when other parts of the skin were again exposed to the lice.