(See also Overview of Bacterial Skin Infections Overview of Bacterial Skin Infections The skin provides a remarkably good barrier against bacterial infections. Although many bacteria come in contact with or reside on the skin, they are normally unable to establish an infection... read more .)
Folliculitis is a type of small skin abscess that involves the hair follicle. Other types of abscesses may appear both on the skin surface and within the deeper structures of the skin without always involving a hair follicle. Most skin abscesses Skin abscesses Folliculitis and skin abscesses are pus-filled pockets in the skin resulting from bacterial infection. They may be superficial or deep, affecting just hair follicles or deeper structures within... read more 
are caused by Staphylococcus aureus bacteria and appear as pus-filled pockets on the skin surface. Recently, a strain of Staphylococcus that is resistant to previously effective antibiotics Antibiotic resistance Bacteria are microscopic, single-celled organisms. They are among the earliest known life forms on earth. There are thousands of different kinds of bacteria, and they live in every conceivable... read more has become a more common cause. This strain is called methicillin-resistant Staphylococcus aureus (MRSA Methicillin-resistant Staphylococcus aureus (MRSA) Staphylococcus aureus is the most dangerous of all of the many common staphylococcal bacteria. These gram-positive, sphere-shaped (coccal) bacteria (see figure ) often cause skin infections... read more 
).
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 live in crowded conditions, 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 Obesity Obesity is excess body weight. Obesity is influenced by a combination of factors, which usually results in consuming more calories than the body needs. These factors may include physical inactivity... read more 
, old age, and possibly diabetes Diabetes Mellitus (DM) Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more 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 their entire body with antibacterial soap, apply antibiotic ointment inside the nose where the bacteria can hide, and take antibiotics by mouth.
Folliculitis
Folliculitis is an infection of a hair follicle. It looks like a tiny red or white pimple at the base of a hair. There may be only one infected follicle or many. Each infected follicle is itchy or 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.
Some people develop mild folliculitis in areas subjected to moisture and friction, such as areas under sports equipment or on the buttocks.
Infected hairs easily fall out or may be plucked out, but new pimples tend to develop.
Sometimes stiff hairs in the beard area (or in any area that is shaved) curl and reenter the skin (ingrown hair) after shaving, causing mild irritation and inflammation. However, there is no actual infection. This type of folliculitis is called pseudofolliculitis barbae Ingrown Beard Hairs Pseudofolliculitis barbae is caused by ingrown hairs, usually in the beard, that become inflamed when the hairs penetrate the skin before they leave the hair follicle or after they leave the... read more 
.
For severe, recurring folliculitis, 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 the choice of antibiotic.
Folliculitis is treated with antibacterial cleansers or antibiotics that are applied directly to the skin (topically). 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 or whirlpool 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. The person may need to temporarily stop shaving.
Skin abscesses
Skin abscesses 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 and carbuncles are types of skin abscesses.
Furuncles (boils) are tender, smaller, more superficial abscesses that by definition involve a hair follicle and the surrounding tissue. Furuncles are common on the neck, breasts, face, and buttocks. They are uncomfortable and may be particularly painful in sensitive areas (for example, on the nose, ear, or fingers).
The furuncle (boil) in this photo is a tender, swollen, pus-filled area.
Photo provided by Thomas Habif, MD.
This woman has a red, inflamed furuncle under her eyebrow.
DermPics/SCIENCE PHOTO LIBRARY
This photo shows a carbuncle found on the back of the neck. It is formed by a cluster of interconnected furuncles, which are painful, pus-filled, inflamed hair follicles.
SCIENCE PHOTO LIBRARY
Carbuncles are clusters of 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.
Doctors diagnose skin abscesses based on their appearance. Sometimes, doctors send pus samples to a laboratory to identify the bacteria (called a culture).
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 and washes out the pocket with a sterile saline solution. Large abscesses over 5 centimeters (about 2 inches) in diameter may require temporary packing with gauze. If the abscess is completely drained, antibiotics usually are not needed. However, antibiotics, taken by mouth, might be given because of the following:
The abscess did not resolve with drainage.
The person has a weakened immune system.
The person has many abscesses.
The person is at risk of developing a heart infection (endocarditis).
The abscess is on the middle part of the face.
The person has fever.
People who have recurring skin abscesses can wash their skin with liquid soap that contains special antiseptics and take antibiotics for 1 to 2 months.
