The head louse is the most common human louse and can be very irritating. Both males and females can latch onto the host and feed on blood. Adult females glue their eggs (the nits) onto shafts of the host person’s hair. The eggs then take around 4–15 days to hatch.
Head lice don’t directly transmit diseases – but they can make you very itchy, and if you scratch at the itches, this can lead to secondary infections.