Folliculitis, Furuncles, and Carbuncles

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
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:

• Trauma
• Chronic friction
• Occlusive clothing
• Occlusive chemicals
• Excessive sweating
• Exposure to water

Pictures of Folliculitis

• Folliculitis on the scalp
• Folliculitis on the leg

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.

Furuncle
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:

• Obesity
• Blood disorders
• Taking oral steroid medications
• Diabetes

Carbuncle
A carbuncle can simply be defined as an extension of a furuncle to multiple follicles. A carbuncle usually involves the deeper layers of the skin - the subcutaneous fat. It looks like a large, red nodule that is indurated and may be fluctuant or have visible layers of pus just beneath the surface of the skin. Carbuncles often occur on the nape of the neck, the back, or the thighs and cause a fever and fatigue. Carbuncles rarely heal on their own and require immediate medical attention.

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.

Carbuncles Caused by Methacillin Resistant Staphylococcus Aureus (MRSA)
In the past several years there has been a sharp increase in the incidence of infections caused by a special strain of S. aureus that is resistant to the normal penicillin-based treatment. Until very recently, MRSA was an uncommon bacterial strain that occurred in nursing homes and other long-term care facilities. But with the overuse of antibiotics for conditions that don't require antibiotics, MRSA infections are common in certain regions of the United States. These infections often occur spontaneously in the groin, buttock, and upper thigh region. Currently there are antibiotics that can be used to treat these infections. The most common antibiotics used are trimethoprim-sulfamethoxazole (Septra or Bactrim) and fluroquinolone antibiotics like levofloxacin (Levaquin) and moxifloxacin (Avelox) in people who are allergic to sulfa.

References
Stulberg, Daniel and Penrod, Marc. "Caring for Common Skin Conditions: Common Bacterial Skin Infections." American Family Physician 66. (July 1, 2002): 119-24.

Tavelli Bert. "Infectious Diseases of the Skin." Noble: Textbook of Primary Care Medicine, 3rd ed. New York: Mosby, 2001. 787-788.

Swartz Morton. "Cellulitis and Subcutaneous Tissue Infections." Mandell: Principles and Practice of Infectious Diseases, 5th ed. London: Churchill Livingstone, 2000. 1039-1040.

Bhumbra, Nasreen and McMullough Sophia. "Skin and Subcutaneous Infections." Primary Care Clinics in Office Practice 30. (March 2003):2-3.

Wilkerson Michael. "Baterial Disaeses of the Skin." Rakel: Conn's Current Therapy, 54th ed. New York: Saunders, 2002. 816.