9 Common Bacterial Skin Infections

Bacterial skin infections are fairly common and can range in severity from mild (albeit annoying) to life-threatening. Most bacterial infections are caused by Staphylococcus aureus (staph) or Streptococcus pyogenes (the same bacteria responsible for strep throat). A bacterial infection can take many different forms depending on its location, type, even the age of the affected individual. Most can be treated by your internist or family physician. More complex ones may require a consultation with a dermatologist or even a rheumatologist. In the most serious cases, a bacterial infection can spread to the bloodstream and cause sepsis, which may be life-threatening.

Here is a rundown of the nine most common bacterial infections and how to identify them:


Cellulitis on the foot.

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Cellulitis affects the two deepest layers of the skin, the dermis and the subcutaneous tissue. It often appears as a swollen, red area on the skin, and feels tender and hot when touched. Cellulitis typically develops in areas where the skin has been broken, such as near ulcers, bruises, burns, or recent surgical wounds. While many types of bacteria can cause cellulitis, Staphylococcus and Streptococcus are the most common culprits. If the cellulitis spreads to your lymph nodes and bloodstream, it can become life-threatening; Seek medical help immediately if you suspect you have this infection.


Erysipelas on leg

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Erysipelas, which is colloquially known as St. Anthony's Fire because of the intense, burning sensation that characterizes it, infects the top two layers of the skin. Symptoms include extreme redness, swelling, and a sharply-defined border between the normal and infected skin tissue. Similar in appearance to cellulitis, which occurs in the lower layers of the skin, erysipelas is caused by Streptococcus bacteria. Minor conditions such as athlete's foot or eczema can also lead to erysipelas, or it can occur when bacteria spreads to the nasal passages following a nose or throat infection.

Bacterial Folliculitis

Folliculitis on a child’s back.

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Bacterial folliculitis is a relatively common infection of the hair follicles, usually caused by a fungus, ingrown hair, or blockages from moisturizers or other products applied to the skin. Shaving or plucking hairs can also increase the risk. Symptoms of bacterial folliculitis include tiny, red bumps or white-headed pimples filled with pus. This infection tends to be more prevalent among people with acne as compared to those who have clear skin. While bacterial folliculitis usually heals on its own without any special treatment, more severe cases may require antibiotics. Left untreated, folliculitis can cause permanent hair loss.

Hot Tub Folliculitis

Hot Tub Folliculitis.

Joel Carillet / Getty Images

Hot tub folliculitis is characterized by pus-filled bumps and an itchy red rash that appears anywhere from a few hours to several days after exposure to the bacteria. Sometimes called “pseudomonas folliculitis” or “Jacuzzi folliculitis" because it is contracted through contaminated whirlpools, hot tubs (especially wooden ones), water slides, physiotherapy pools, or even loofah sponges, hot tub folliculitis typically occurs on the chest or areas under a swimsuit, where water and bacteria have been trapped for a period of time. It is caused by the Pseudomonas aeruginosa bacteria, which can even survive in chlorinated water, making it tougher to kill. Not surprisingly, children are more prone to hot tub folliculitis because their skin is thinner, and they tend to stay in water longer than adults do. Hot tub folliculitis is also more common in people with acne or dermatitis, both of which make the skin conducive to bacterial penetration.


A furuncle.

Mahdouch / Wikimedia Commons / CC BY 1.0

A furuncle, more commonly known as a boil, is a painful infection that forms around a hair follicle. It begins as a red lump, which may be tender, and rapidly fills with pus as it becomes enlarged. If left untreated, a furuncle can develop into an abscess. Unlike folliculitis, which also involves infection of a hair follicle, a furuncle is an infection of the entire pilosebaceous unit. Pilosebaceous units, which are located throughout the body (except on the palms, soles of the feet, and lower lip), comprise the shaft, follicle, sebaceous gland, and arrector pili muscle (a bundle of small muscle fibers attached to a hair follicle). Furuncles are commonly found on the face, neck, armpits, buttocks, and thighs. Applying warm compresses can help drain a furuncle of pus, but In severe cases, it may have to be lanced in the doctor's office.



Drvgaikwad/Wikimedia Commons / CC BY 3.0

A carbuncle is a cluster of several furuncles densely packed together. It can be as large as four inches across horizontally, and usually has one or more openings from which pus may ooze onto the skin. Carbuncles usually develop on the back, thighs, or back of the neck, and the infection tends to be deeper and more severe than those caused by furuncles. The most common cause of a carbuncle is the staph bacteria. Sometimes, the infection is accompanied by fever and general weakness and exhaustion. The risk of scarring is higher with a carbuncle infection, and it may take longer to develop and resolve than furuncles. For this reason, carbuncles often require medical attention. They are contagious and can spread to other parts of the body, and to other people,


Impetigo on child's mouth

CFCF / Wikimedia Commons / CC BY 4.0

Impetigo is a bacterial infection of the top layer of epidermal skin It is highly contagious and more commonly seen in children than adults. Caused by Streptococcus and Staphylococcus, the hallmark of impetigo is a honey-colored crust. The sores associated with this bacterial infection usually occur around the nose and mouth but can spread to other parts of the body through skin-to-skin contact, clothing, and towels. Impetigo is usually treated with a topical antibiotics.


Erythrasma on armpit

Caliendo / Custom Medical Stock Photo

Erythrasma is a superficial skin infection caused by the Corynebacterium minutissimum bacteria. Initially symptoms include skin lesions of well-defined pink patches covered with fine scales and wrinkling that become red, then brown and scaly. Erythrasma develops in areas where skin touches skin, such as the armpits, groin, or between the toes. Due to its location and appearance, it's often confused with fungal infections like athlete's foot and jock itch. People with erythrasma are usually asymptomatic, but mild itchiness or burning may be present, especially if the infection is located in the groin area. Erythrasma commonly develops in warm, humid climates, or as a result of poor hygiene, sweating, obesity, diabetes, advanced age, or poor immune function.

MRSA Skin Infections

A MRSA skin infection

CDC / Bruno Coignard, M.D.; Jeff Hageman, M.H.S. / Wikimedia Commons / Public Domain

Methicillin-resistant Staphylococcus aureus (MRSA) is a serious bacterial infection that is resistant to standard antibiotic treatment. It will often cause a mild, ulcerative sore on the skin and can sometimes lead to serious infections. In these cases, MRSA can spread through the bloodstream to infect other organs, such as the lungs or urinary tract. The symptoms of a MRSA infection depend on the part of the body that is infected, and may include redness, swelling, pain, pus, or fever. Some MRSA infections visually look like other bacterial skin infections, and can even be confused with a spider bite. Laboratory tests are usually required to accurately diagnose MRSA. If left untreated, systemic MRSA can easily spread from person-to-person, and may be contracted in the hospital following surgery.

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