Folliculitis and skin abscesses are pus-filled pockets in the skin resulting from bacterial infection. They may be superficial or deep, affecting just hair follicules or deeper structures within the skin.
Folliculitis is a type of skin abscess that involves the hair follicle. Abscesses may appear both on the skin surface and within the deeper structures of the skin without always involving a hair follicle. Most abscesses are caused by Staphylococcus aureus bacteria (see Bacterial Infections: Staphylococcus aureus Infections) and appear to be pus-filled pockets on the skin surface. Recently, a strain of Staphylococcus has appeared that is resistant to previously effective antibiotics. This strain is called methicillin-resistant Staphylococcus aureus (MRSA). 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 folliculitis or skin abscesses. A weakened immune system, obesity, old age, and possibly diabetes are also common risk factors. 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 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, causing irritation without substantial infection. This type of folliculitis is called pseudofolliculitis barbae (see see Hair Disorders: Ingrown Beard Hairs).
Folliculitis is treated with antibacterial cleansers or topical antibiotics. Large areas of folliculitis may require antibiotics taken by mouth. Hot-tub folliculitis goes away in a week without any treatment. However, adequate chlorination of the hot tub is necessary to prevent recurrences and to protect others from infection. Folliculitis caused by ingrown hairs is treated by a number of methods with varying success. For severe, recurring problems, doctors may take a bacterial culture (a sample of pus is sent to a laboratory and placed in a culture medium that allows microorganisms to grow). The results of the culture are used to guide choice of antibiotic. The person may need to temporarily stop shaving.
Skin abscesses, also called boils, are warm, painful, pus-filled pockets of infection below the skin surface that may occur on any body surface. Abscesses may be one to several inches in diameter. Furuncles are smaller, more superficial abscesses that by definition involve a hair follicule and the surrounding tissue. Carbuncles are multiple furuncles that are connected to one another below the skin surface. If not treated, abscesses often come to a head and rupture, discharging a creamy white or pink fluid. 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 skin abscess may go away with application of warm compresses. Otherwise, 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 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 risk that the infection will spread to the brain. Antibiotics also are needed if the infection has spread or if the person has a weakened immune system.
People who have recurrent skin abscesses can wash their skin with liquid soap that contains special antiseptics, or they can take antibiotics for 1 to 2 months.
Last full review/revision October 2007 by A. Damian Dhar, MD, JD