There are four different kinds of skin infections: bacterial, viral, fungal, and parasitic. See examples of each below:

• Bacterial: Impetigo, cellulitis
• Viral: Shingles, measles, chickenpox, herpes simplex, warts, molluscum contagiosum
• Fungal: Ringworm, jock itch, athlete’s foot, yeast infection
• Parasitic: Lice, scabies, bedbugs

Impetigo is a highly contagious bacterial skin infection that most frequently occurs in infants and children but also affects adults. It is caused by Staphylococcus aureus or Streptococci pyogenes (better known as staph or strep) bacteria and spread through skin-to-skin contact.

Impetigo usually appears as red sores or blisters on the face, especially around the nose and mouth, and on the hands and feet. Often there are small blisters with a honey-colored crust or large pus-filled blisters.

Impetigo is treated with an antibiotic ointment such as mupirocin (bactroban), which is effective in 90 percent of cases. Sometimes oral antibiotics are needed.

Cellulitis is a deeper bacterial infection in the skin that typically occurs when bacteria enter through a break in the skin such as a cut or scrape. It can be caused by many types of bacteria but most commonly by Staphylococcus and Streptococcus.

The affected area of skin is usually swollen, red, warm, and painful to the touch. Other symptoms include fever, chills, or sweats. Enlarged lymph nodes can also occur.

Cellulitis is treated with oral antibiotics although IV antibiotics may be required for severe cases.

Ringworm is the generally accepted layman’s term for fungal infections of the skin. The medical term for it is “tinea.”

Ringworm is a misnomer because it is not caused by a worm, but a fungus. It gets the name ringworm because the fungus makes round marks on the skin, often with flat centers and raised borders, like a ring.

There are several different types of ringworm classified according to where it occurs:

• Tinea capitis: This type of ringworm appears on the scalp.
• Tinea corporis: This type of ringworm occurs on the neck, chest, abdomen, back, legs, or arms.
• Tinea cruris: This type of ringworm appears around the groin, inner thighs, and sometimes the buttocks; also known as jock itch.
• Tinea pedis: This type of ringworm occurs on the feet; also known as athlete’s foot.
• Tinea unguium: Also called onychomycosis, this type of fungus grows on fingernails or toenails; it often affects the big toe.

Tinea capitis is ringworm of the scalp. It most frequently occurs in infants and children and is highly contagious. It causes white, fine scaling on the scalp. Sometimes you can see small bald spots with broken hairs.

Tinea capitis is most frequently caused by Microsporum and Trichophyton fungi. Sometimes a provider will use a black light to see if the hair shaft fluoresces, which can be helpful in diagnosing the Microsporum type. Sometimes a provider may scrape the skin to check for microscopic evidence of the fungus.

Trichophyton is more common in the US and is passed from person to person. The Microsporum type is passed from animal to human.

Scalp ringworm is treated with oral antifungal pills (terbinafine, itraconazole, or fluconazole). Your doctor will also prescribe an antifungal shampoo to help prevent the spread of infection.

Tinea corporis is ringworm that typically appears on the neck, chest, stomach, back, arms, or legs. It looks like round lesions with reddish scaling and a central clearing or a raised border. You may see hair loss in areas such as the arms or legs.

Trichophyton rubrum (T. rubrum) is the most common cause. Infection often comes from the feet (tinea pedis) or nails (tinea unguium) originally. Microsporum canis (M. canis) from cats and dogs, and T. verrucosum, from farm cattle, can occur as well.

Ringworm is usually diagnosed with a skin scraping that the provider examines under a microscope. Sometimes skin biopsies are required.

Ringworm is treated with a topical antifungal cream. Occasionally, oral antifungals are needed for stubborn cases or extensive skin involvement.

Jock itch is a nickname for tinea cruris. It appears as an itchy, brownish or reddish rash in the groin, inner thighs, and sometimes the buttocks. It is most common in men and adolescent boys and is typically caused by friction from clothes and prolonged moistness in the groin area, such as from sweating.

Jock itch is treated with a topical antifungal cream. You should wash the area with soap and water and wear loose-fitting cotton undergarments.

Athlete’s foot, the most common fungal skin infection, is a nickname for tinea pedis. It may present as a cracking and rawness in between toes, redness and scaling of the bottom of the feet in a moccasin pattern, or, less frequently, blistering of the feet with redness and scaling.

Athlete’s foot is common in people who go barefoot in public places where the infection can spread, such as locker rooms, showers, and swimming pools. It is treated with a topical antifungal cream. Rarely, oral medication is needed.

This fungal infection is caused by overgrowth of a yeast called Malassezia that normally lives on the surface of the skin. It causes uneven white or light tan-colored circular patches, often scaly, on the neck, chest, back, or arms. Most people get tinea versicolor as teenagers or young adults, except those who live in tropical climates may get it at any age.

The goal of treatment is to reduce the lesions and keep them from flaring up. Treatments may include selenium-based shampoos, topical antifungal creams, and short courses or single-dose regimens of oral antifungal medications.