Pus is a whitish-yellow or yellow substance prouced during inflammatory responses of the body that can be found in regions of pyogenic bacterial infections. An accumulation of pus in an enclosed tissue space is known as an abscess. A visible collection of pus within or beneath the epidermis, on the other hand, is known as a pustule or pimple. Pus is produced from the dead and living cells which travel into the intercellular spaces around the affected cells.