Skin infections are very common occurrences throughout life. Some infections are self-limiting and resolve on their own, but many others require medical attention. Bacterial skin infections technically have specific names based on their origin and extent, but even in the medical community we often lump these technical terms into the common term “boil” or “abscess”. This article will clarify the technical terms we use to describe the diagnosis of specific bacterial infections caused mainly by the bacteria, Staphylococcus aureus.

Folliculitis is an infection that is localized to the hair follicle. A folliculitis looks like small, yellow pustules that are confined to the hair follicle. Factors that can lead to the development of a folliculitis include:

Chronic friction
Occlusive clothing
Occlusive chemicals
Excessive sweating
Exposure to water

Hot Tub Folliculitis
A special case of folliculitis that is not caused by S. aureus is hot tub folliculitis. This self-limited infection is caused by Pseudomonas aeruginosa contracted from hot tubs, whirlpools, and pools with inadequate chlorine levels.

A furuncle is an infection of the pilosebaceous unit, therefore is more extensive than a folliculitis because the infection also involves the sebaceous gland. A furuncle frequently occurs on the neck, face, armpits, and buttocks. It begins as a small, tender, red nodule that becomes painful and fluctuant. Frequently, pus will spontaneously drain, and often the furuncle will resolve on its own.

Factors that contribute to the development of furuncles include:

Blood disorders
Taking oral steroid medications
A carbuncle can simply be defined as an multiple furuncles grouped together. A carbuncle usually involves the deeper layers of the skin – the subcutaneous fat. It looks like a large, red nodule that is hot and may have visible layers of pus just beneath the surface of the skin.

More about carbuncles
Treatment of Folliculitis, Furuncles, and Carbuncles
Mild cases of folliculitis and small furuncles may heal on their own with good hygiene and wound care. More extensive furuncles and all carbuncles need to be treated with antibiotics such as dicloxacillin or cephalexin. If pus or induration are present, in addition to antibiotics, a procedure called incision and drainage (I&D) should be performed to drain the pus and allow the lesion to heal from the inside out.

Dr. Lawrence Jaeger of New York is an expert in the diagnosis and treatment of skin conditions and is board certified in dermatology and dermatologic surgery.