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Skin Infections

There are four types of skin infections: viral, bacterial, fungal, and parasitic. They can range from mild to severe, harmless to serious. The skin is our first line of defense against infections. When the skin is healthy it protects us against infection.

Bacterial skin infections

The most common bacterial infections are caused by staphylococcus (staph) and streptococcus (strep). These bacteria normally live on the skin and cause no problems until there is an injury allowing the bacteria into the skin.

Bacteria infect the skin through hair follicles and breaks in the skin caused by preexisting skin conditions, a puncture or scrape, a surgical wound, an insect or animal bite, a burn, or sunburn.

Some infections remain in the skin and others carry the risk to go into deeper tissues.

Skin infections can also develop from bacteria that are picked up from the soil, a contaminated pond, the ocean, or the hospital. MRSA is a common staph bacterium that causes skin infections in communities and hospitals but is resistant to many commonly used antibiotics and can be difficult to treat.

Minor skin infections can cause a rash, a boil (a painful pus-filled lump), or an abscess (a pocket of pus). Severe skin infections can destroy the infected tissues and cause a high fever and intense pain.

Some people are at particular risk of bacterial skin infections, including people with diabetes, older individuals, those living in a nursing home, patients with HIV/AIDS or hepatitis, those with cancer undergoing chemotherapy, or people who have medical conditions that suppress the immune system.

Bacterial skin infections are treated with antibiotics either oral, topical or both; and in the most severe cases Intravenous antibiotics may be necessary. Abscesses can be drained, and if need be, dead skin and tissues can be removed in a procedure called debridement.


Impetigo is common, contagious skin infection, most common in children, caused by staph and strep that creates honey yellow, crusted sores and small fluid-filled blisters on the face, arms, and legs. The lesions are itchy and painful. Scratching can spread the infection.


Cellulitis is common infection of the deep layers of the skin. The infection spreads from the surface of the skin to the deeper layers causing redness, pain, swelling and heat, and can permanently damage the skin. It is often caused by strep or staph.


Folliculitis is an infected and inflamed hair follicle. It can appear as tiny red or white pimples at the base of one or more hair follicles. It can itch and may be painful.  The infected hair may fall out. In severe cases skin abscesses can form below the skin. Folliculitis is common in people with acne and shaving increases the risk of folliculitis. Often it resolves without treatment, but severe infection can cause permanent hair loss.

Fungal infections

Fungi live on the body where it is moist and warm such as skin folds, between the toes, on the genitals and under the breasts. The fungi live on the skin and rarely penetrate deeply.

Fungal infections can cause rashes in areas of infection and on other parts of the body. . Fungal infections are diagnosed by skin scraping and cultures. They are treated with topical and oral anti fungal medications.

Ringworm is a fungal infection that spreads easily from skin-to-skin contact. It typically presents as a circular shaped rash. It can affect the feet (athlete’s foot), groin (Jock itch), scalp, hands, toenails and fingernails.

Fungal nail infections occur when the fungus attacks a fingernail, toenail or the nail bed. It is notoriously difficult to cure, and recurrence is common. Treatment courses with topical or oral medications are long, ranging from 3-12 months.

Viral skin infections

A virus is smaller than a fungus or bacterium. It can only infect the skin if it invades a living skin cell. Inside the cell it replicates and takes control of the infected cells. Viral skin infections cause warts, shingles, herpes (cold sores), and other rashes. The integrity of the skin barrier can keep viruses out. If the virus gets into the cells, it triggers an immune system response. Additionally, many virus can cause immune reactions that present as rashes, though don’t directly infect the skin cell.

Cold sores are caused by the herpes simplex virus. Cold sores occur most commonly on the inside and outside of the mouth, but can infect any area of the body.

Shingles is a viral infection of the chickenpox virus called the varicella virus. It can be extremely painful and debilitating. Shingles is a re-activation of the chickenpox virus that sits dormant in our nerves after a chicken pox infection but can reactivate due to numerous reasons.

Parasitic skin infections

Parasites are tiny insects or worms that burrow into the skin to live or lay their eggs and live off the human host. Parasitic infections are usually confined to the outer layer of skin. Bedbugs are parasites. Scabies is caused by a mite that burrows into the skin.  Lice are insects that cling to hair follicles. They can infect the hair on the head, body, and pubic area. All parasitic infections are easily spread. They are treated with anti parasitic medications.

When you have a rash or unexplained itching and inflammation, contact Dr. Michael Sotiriou at Salt Lake Dermatology & Aesthetics in Salt Lake City Utah. He is leader in the field of dermatology and can identify your skin infection and offer curative treatments.

At a Glance

Dr. Michael Sotiriou

  • Board-certified, Residency-Trained Medical and Cosmetic Dermatologist
  • Sub-Specialty Board Certification in Mohs Micrographic Dermatologic Surgery from the American Board of Dermatology
  • Fellow of the American Academy of Dermatology
  • Learn more

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