Final answer:
Lice and scabies are the most common parasitic infestations seen by barbers in barbershops, often spread through close personal contact or by sharing personal items.
Step-by-step explanation:
The two most common parasitic infestations barbers may see in the barbershop are lice and scabies. Lice, which include the head louse (Pediculus humanus capitis), body louse (Pediculus humanus corporis), and the crab louse or pubic louse (Pthirus pubis), are often associated with humans and can be spread through close personal contact or contact with infested items. Scabies, which are caused by mites that burrow into the skin to lay eggs, can also be spread through close physical contact or by sharing clothing, towels, or bedding with someone who has scabies. While scabies and lice infestations can occur in various settings, barbershops are potential sites for their transmission due to the close proximity between the barber and clients.