Are booklice harmful to humans?

Booklice do not bite people or feed on human blood. These tiny insects usually feed on mould and other organic material in damp places, rather than living on a person like parasitic lice. They are mainly a nuisance indoors, although they can contaminate stored food and occur on damp books or other materials. (Iowa State: Booklice; extension.umd.edu)

Finding booklice is a reason to check humidity, leaks and damp storage. Drying affected areas and reducing moisture tackles the conditions they need. Do not assume unexplained skin marks are booklice bites just because tiny insects are nearby; confirm the insect and consider other causes if irritation continues. (Iowa State: Booklice; extension.umd.edu)