Combs are currently a useless item, and often considered as junk.
Combs have no use, being added purely for the purpose of clutter, creating more realism for the player when looting.
Combs can be found in bathroom counters, medicine cabinets, hair salons and corpses.
From newitems.txt (Project Zomboid directory/media/scripts/)
Weight = 0.2,
Type = Normal,
DisplayName = Comb,
Icon = Comb,