Bacterial Skin Infections

An itching skin condition on an elbow and all over the arm.
Bacteria that touch your skin are more likely to infect you if your skin is broken. See more pictures of skin problems.
Š Lisjak

Although bacteria can often touch or live on the skin without causing an infection, the risk of getting a bacterial skin infection becomes much higher when the skin is broken. People who have certain medical conditions, including diabetes, acquired immune deficiency syndrome (AIDS) or skin damage from sunburn, are also more likely to be at risk. Many different types of bacterial infections can enter through the skin, but a few are more frequent than others.

Cellulitis, an infection beneath the skin's surface, normally happens after a break in the skin, such as a surgical incision, cut, wound or insect bite [source: Stulberg]. Those at risk for cellulitis include people who have weak immune systems or who handle fish, meat, poultry or soil without wearing gloves [source: WebMD].


Folliculitis, an infection of the hair follicles, happens because the follicles have been damaged. Improperly treated pools or hot tubs, shaving, tight clothing, and bacteria from nearby scrapes and cuts can all cause folliculitis [source: WebMD].

Boils and carbuncles are also infected hair follicles, but they are usually much deeper [source: Stulberg]. These red, pus-filled bumps are called boils when only one is present or carbuncles when they form in groups.

Impetigo can develop if you have a cut or an insect bite, but it also can occur in previously healthy skin [source: Mayo Clinic]. The condition, marked by sores on the face, usually occurs in young children and is very contagious. Adults can also get impetigo if a wound or break is present on the skin.

Bacterial skin infection symptoms run the gamut from barely noticeable to life-threatening -- read on to find out how to tell the difference and when you should worry.


Bacterial Skin Infection Symptoms

Bacteria are responsible for causing a range of unsightly skin conditions, including cellulitis, folliculitis, impetigo, and boils and carbuncles, but these conditions are usually fairly easy to spot. Boils, redness, rashes and other irritation on the skin's surface might mean you need to seek medical attention.

Cellulitis forms deep in the skin's layers and can cause skin to swell, turn red and be warm and tender [source: Mayo Clinic]. Symptoms usually surface in the legs, fingers, toes, face, feet, hands, torso, neck and buttocks, but can occur anywhere [source: Stulberg]. Infection signs include swelling, bruising, chills and overall weakness. If you have more severe symptoms, including a large area of infected skin, fever, numbness, or infection near your eyes or ears, or if you have HIV or diabetes, consult a doctor as soon as you suspect an infection [source: University of Virginia Health System].


Small, white lumps around hair follicles can be a sign of folliculitis. These bumps also may begin as sore, red lumps but can become more serious if they take over a large area of skin. The blisters eventually fill with pus and break open, which can cause scarring [source: Mayo Clinic].

Signs that you may have impetigo include sores, usually found around the nose or mouth, that begin as red spots and progress to larger, itchy blisters. These sores can become a concern if they continue to increase in size and number [source: WebMD]. Once they break open, the sores may form a yellow-brown crust.

Boils and carbuncles begin as red lumps that grow larger and fill with pus before breaking open and draining. A boil, or furuncle, is a bacterial infection in a hair follicle. A group of these that form a connected area of infection is called a carbuncle [source: Mayo Clinic]. Boils are frequently found on the face, neck, armpits, buttocks or thighs. Carbuncles, frequently found on the back of the neck, shoulders or thighs, result in a deeper, more severe infection. Consult a doctor if you have boils that are on your face or spine, occur frequently or with a fever, or aren't showing signs of healing, or if you have red lines on your skin around the boil.

Concerned about catching an infection? Read on to discover ways to protect your skin from potential problems.


Bacterial Skin Infection Causes

Although the bacteria that cause them may vary, bacterial skin infections often are the result of skin that has been wounded, scraped or cut open. This opening in the body's natural barrier allows bacteria to enter and grow, causing the infection. Those with certain medical conditions, including diabetes and AIDS, also are at greater risk of infection. Healthy people can still develop infections, although it is less common.

People who leave their hands exposed while working with bacteria-contaminated materials, such as meat and poultry, are at particular risk for cellulitis [source: WebMD]. It is usually caused by one of two of the most common strains of bacteria: Streptococcus pyogenes (strep) or Staphylococcus aureus (staph). This infection can appear either on its own or as a result of a wound or cut that becomes infected.


Folliculitis tends to strike those who use poorly maintained pools or hot tubs, wear tight clothing, overuse antibiotics or steroid creams, or have existing infected injuries or wounds [source: WebMD]. Folliculitis is normally caused by the bacteria Staphylococcus.

Boils or carbuncles tend to strike people who are in close proximity to someone who is infected, those who already have other skin conditions such as acne or dermatitis or those who have a weakened immune system [source: Mayo Clinic]. Poor hygiene also can contribute to boil or carbuncle infections, which are caused by the bacteria Staphylococcus [source: WebMD].

Impetigo most commonly affects infants in addition to children between the ages of 2 and 6, but adults can also get it. You are more likely catch impetigo if you have skin-to-skin contact with an infected person, have contact with an towels or clothing used by an infected person, or have pre-existing skin conditions [source: Mayo Clinic]. Conditions that have already irritated skin, including eczema, poison ivy, burns or bug bites, make it easier for the bacteria to enter [source: WebMD]. Impetigo can be caused by either Staphylococcus or Streptococcus.

The good news is that treatments are available. Read on to learn what can be done to clear up infections.


Bacterial Skin Infection Treatments

Treatment of bacterial skin infections will depend on their severity. For a small occurrence of some infections, for example, an at-home treatment might be enough. However, for contagious or more widespread infections, medical treatment may be necessary.

Cellulitis should be treated by a doctor because it can spread to other areas of the body, including the brain if the infection is present on the face [source: WebMD]. Treatment includes:


  • Antibiotics
  • Applying warm, wet dressings to the infected area
  • Rest
  • Elevating the infected area if possible

Mild infections are normally treated at home with antibiotic pills, but more severe infections might require intravenous antibiotics delivered at a hospital [source: WebMD].

Mild folliculitis normally clears up in less than two weeks, but you can apply warm compresses to help relieve itching [WebMD, Mayo Clinic]. If there's no change after three days or if the infection appears to have spread, you should seek a doctor's help. More severe infections require antibiotics.

To clear up a pesky boil, apply a warm, wet compress to the area, which will bring the pus to the surface. Do not pop the boil; instead, wait for it to burst on its own because interference can make the infection worse [source: WebMD]. Be sure to wash the wound regularly with antibacterial soap until it heals. A doctor may be able to drain large boils or carbuncles surgically, which can reduce scarring. The doctor also might prescribe antibiotics to help with infections that are severe or difficult to eliminate [source: Mayo Clinic].

Impetigo requires treatment by a doctor because it can be contagious. Treatment includes an antibiotic cream for mild infections or antibiotic pills for more severe infections. With proper treatment, the sores will generally heal in about seven days. You are usually not considered contagious if you have been under treatment for 48 hours or more [source: WebMD].

Wondering which of these infections is contagious? Read on to find out.


Contagious Bacterial Skin Infections

So, when should you worry about catching or passing a skin infection to others? Cellulitis, for example, is very difficult to catch from an infected person. Although it is possible, the other person's infection would have to directly touch your skin, and then the bacteria would have to spread to an opening on your skin, making it an unlikely situation [source: Steckelberg].

The bacteria that cause folliculitis can be passed from person to person if proper hygiene is not practiced. Do not share towels with others, and use a clean towel each time you bathe if you do have an infection. Avoid scratching the affected area, because your hands can then transfer the bacteria elsewhere [source: WebMD].


Close contact with a person who has a boil or carbuncle can cause you to be infected by the same bacteria. To avoid infection, practice proper hygiene by washing your hands frequently, keeping your infections covered and not sharing personal items [source: Mayo Clinic].

Impetigo is one of the more contagious bacterial skin infections. Those who are infected should stay home and avoid contact with others to keep from spreading the disease. It also is important to avoid sharing items, such as towels, clothing and pillows, that could transfer bacteria to an uninfected person [source: WebMD]. If necessary, cover the infected area to keep from scratching, because this can transfer the infection to other people or to other parts of your body. Washing your hands frequently or wearing gloves when you're around an infected person also can help stop the spread of infection [source: Mayo Clinic].

Bacterial skin infections can range from a nuisance to downright nasty, but by practicing good hygiene and seeking medical advice when appropriate, you can limit the toll they take on your skin. To learn more, visit the links on the next page.


Lots More Information

Related HowStuffWorks Articles


  • Berman, Kevin, M.D., Ph.D. "Hair Follicle Anatomy." MedlinePlus. Nov. 13, 2006. (Accessed 8/1/09)
  • New Zealand Dermatological Society Inc. "Bacterial Skin Infections." July 24, 2009. (Accessed 8/1/09)
  • Mayo Clinic. "Boils and Carbuncles." Oct. 18, 2008. (Accessed 8/1/09)
  • Mayo Clinic. "Cellulitis." Jan. 15, 2008. (Accessed 8/1/09)
  • Mayo Clinic. "Folliculitis." Oct. 5, 2007. (Accessed 8/1/09)
  • Mayo Clinic. "Impetigo." Oct. 4, 2008. (Accessed 8/1/09)
  • Steckelberg, James M, M.D. "Is Cellulitis Contagious?" Mayo Clinic. Feb. 6, 2008. (Accessed 8/1/09)
  • Stulberg, Daniel L, M.D.; Marc A. Penrod, M.D.; and Richard A. Blatny, M.D. "Common Bacterial Skin Infections." American Family Physician 66:119-24. July 1, 2002. (Accessed 8/1/09)
  • University of Virginia Health System. "Bacterial Skin Infections." Feb. 12, 2004. (Accessed 8/1/09)
  • WebMD. "Boils." Aug. 10, 2005. (Accessed 8/1/09)
  • WebMD. "Cellulitis." March 22, 2007. (Accessed 8/1/09)
  • WebMD. "Folliculitis." June 26, 2007. (Accessed 8/1/09)
  • WebMD. "Impetigo." Aug. 4, 2008. (Accessed 8/1/09)