During times of relaxation, a chimpanzee may often be found grooming another chimpanzee or its own hair. The most obvious function is the removal of pieces of debris from soil, vegetation and dried skin or parasites from the hair. The chimpanzee uses one hand to hold the hair back while the other hand, lips, or teeth are used to pick out and remove the small pieces of debris.
Grooming is also used to relax tension from threats and aggression. It helps to maintain friendly ties among family and community members and to lessen the stress of infants during weaning. A chimpanzee may request or solicit grooming by approaching another chimpanzee and getting their attention by presenting a part of its body for grooming. It may scratch itself or start to groom itself. Grooming is a very important social and skin care behaviour. A grooming session may include several individuals of varying ages and continue for a few seconds, minutes, or hours.