February 09, 2007



Erythrasma is infection of the top layers of the skin caused by the bacterium Corynebacterium minutissimum.

Erythrasma affects mostly adults, especially those with diabetes; it is most common in the tropics. Erythrasma often appears in areas where skin touches skin, such as under the breasts and in the armpits, webs of the toes, and genital area—especially in men, where the thighs touch the scrotum. The infection can produce irregularly shaped pink patches that may later turn into fine brown scales. In some people, the infection spreads to the torso and anal area.

Although erythrasma may be confused with a fungal infection, doctors can easily diagnose erythrasma because skin infected with Corynebacterium glows coral red under an ultraviolet light.

An antibiotic given by mouth, such as erythromycin or tetracycline , can eliminate the infection. Antibacterial soaps, such as chlorhexidine, may also help. Topical drugs such as clindamycin and miconazole cream are also effective. Erythrasma may recur in 6 to 12 months, necessitating a second treatment.

Folliculitis, Skin Abscesses, and Carbuncles
Folliculitis, skin abscesses, and carbuncles are pus-filled pockets in the skin resulting from bacterial infection.

Most skin infections involving pus-filled pockets are caused by Staphylococcus aureus bacteria (see Bacterial Infections: Staphylococcal Infections). Sometimes the bacteria enter the skin through a hair follicle, small scrape, or puncture, although often there is no obvious point of entry. People who have poor hygiene or chronic skin diseases or whose nasal passages contain Staphylococcus are more likely to have episodes of these skin infections. Some people may have recurring episodes of infection for unknown reasons.

Doctors may try to eliminate Staphylococcus from people prone to recurring infections by instructing them to wash the entire body with antibacterial soap, apply antibiotic ointment inside the nose, and take antibiotics by mouth.

Folliculitis, skin abscesses, and carbuncles differ in the size and depth of the pus-filled pockets.

Folliculitis: Folliculitis is an infection of a hair follicle. It looks like a tiny white pimple at the base of a hair. There may be only one infected follicle or many. Each infected follicle is slightly painful, but the person otherwise does not feel sick.

Some people develop folliculitis after exposure to a poorly chlorinated hot tub or whirlpool. This condition, sometimes called "hot-tub folliculitis" or "hot-tub dermatitis," is caused by the bacterium Pseudomonas aeruginosa. It begins anytime from 6 hours to 5 days after the exposure. Areas of skin covered by a bathing suit, such as the torso and buttocks, are the most common sites.

Sometimes stiff hairs in the beard area curl and reenter the skin (ingrown hair) after shaving, producing irritation without substantial infection. This type of folliculitis (pseudofolliculitis barbae) is particularly common in black men.

Folliculitis is treated with warm compresses. Sometimes, topical antibiotics with mupirocin or clindamycin are applied 2 to 3 times per day. Large areas of folliculitis may require antibiotics, such as dicloxacillin or cephalexin , taken by mouth. Hot-tub folliculitis goes away in a week without any treatment. Folliculitis caused by ingrown hairs is treated by a number of methods with varying success. For severe, recurring problems, shaving may need to be discontinued.

Skin Abscesses: Skin abscesses, also called boils or furuncles, are warm, painful pus-filled pockets of infection below the skin surface. Abscesses may be from one to several inches in diameter. If not treated, they often come to a point and rupture. Bacteria may spread from the abscess to infect the surrounding tissue and lymph nodes. The person may have a fever and feel generally sick.

A doctor treats an abscess by cutting it open and draining the pus. After draining the abscess, a doctor makes sure all of the pus has been removed by washing out the pocket with a sterile salt solution. Sometimes the drained abscess is packed with gauze, which is removed 24 to 48 hours later.

If the abscess is completely drained, antibiotics usually are not needed. However, if the infection has spread or if the abscess is on the middle or upper part of the face, antibiotics that kill staphylococci, such as dicloxacillin and cephalexin, may be used because of the high risk that the infection will spread to the brain.

Carbuncles: Carbuncles are clusters of small, shallow abscesses that connect with each other under the skin. Multiple areas may open and drain pus spontaneously. The person often has a fever and feels fatigued and sick. Carbuncles are more common in men and usually occur on the back of the neck. They often result in extensive peeling of skin and scar formation. Older people, people with diabetes, and people with serious medical disorders are more prone to carbuncles.

Treatment is with antibiotics taken by mouth. Any large abscesses are cut open to allow pus to drain. Carbuncles are hard to eliminate because many small pus-filled pockets are difficult to find and drain. Therefore, antibiotics must sometimes be continued for several months.

Adapted from: Merck & Co., Inc