Scratching can cause crusting and scaling on the scalp. Occasionally secondary bacterial infection of the scalp results in small sores on the scalp with tender glands in the neck. Dermatitis can also occur with a heavy infestation of lice. Fortunately head lice are not known to carry any diseases which can affect humans. Lice are around 3mm in length and can be seen moving from hair to hair.
Unhatched eggs have a dark area within the shell while hatched eggs are transparent.
Occasionally the eyelashes can become infested. Prioderm Cream Shampoo Derbac-M Cream Shampoo Pyrethrins are naturally occurring insecticides found in some flowers such as the chrysanthemums. In high doses they can be toxic to humans. Permethrin is a synthetic compound, which is as effective as pyrethrin but has much less toxicity. Even so, a small portion may be absorbed into the body and for this reason it is important to follow the manufacturer's advice on how long to use it.