Skin Infections

Overview

A skin infection occurs when germs get past the skin's protective barrier and multiply in the skin or the tissue beneath it. The skin is the body's largest organ and its first line of defense, so breaks from cuts, scratches, bites, surgery, or other conditions can open the door to infection.

Skin infections are grouped by the type of germ that causes them: bacterial (such as cellulitis and impetigo), fungal (such as ringworm and athlete's foot), viral (such as warts and cold sores), and parasitic (such as scabies). Most are mild and respond well to treatment, but some can spread quickly and become serious, especially in people with weakened immune systems or diabetes.

Symptoms

Symptoms vary by the type and depth of infection, but common signs include:

• Redness, swelling, or warmth of the skin
• Pain, tenderness, or itching in the affected area
• A rash, blisters, sores, or pus-filled bumps
• Scaling, flaking, or cracked skin (common with fungal infections)
• Crusting or oozing

Signs that an infection may be becoming serious include rapidly spreading redness, increasing pain out of proportion to how the area looks, red streaks moving away from the wound, fever or chills, and the skin turning purple, gray, or black. These warning signs need prompt medical attention.

Causes

Different germs cause different kinds of skin infection:

• Bacteria: Staphylococcus and Streptococcus are the most common culprits, causing infections such as cellulitis, impetigo, boils, and abscesses. Some strains, like MRSA, resist common antibiotics.
• Fungi: Dermatophytes and yeasts thrive in warm, moist areas and cause ringworm, athlete's foot, jock itch, and yeast infections.
• Viruses: Viruses cause warts, cold sores (herpes simplex), shingles, and molluscum contagiosum.
• Parasites: Tiny mites or lice cause scabies and lice infestations.

Infection usually starts when germs enter through a break in the skin or overgrow in a warm, damp environment.

Risk Factors

• Cuts, scrapes, bites, burns, or surgical wounds
• Diabetes or poor circulation
• A weakened immune system from illness or medication
• Skin conditions such as eczema that damage the skin barrier
• Excessive moisture, sweating, or warm, humid environments
• Close contact in crowded settings or sharing personal items
• Obesity, which creates skin folds where germs grow

Diagnosis

Doctors often diagnose a skin infection by examining the affected area and asking about symptoms, recent injuries, and exposures. When the cause is unclear or the infection is severe, additional tests may be used:

• Skin swab or culture: A sample of pus or fluid is tested to identify the germ and guide antibiotic choice.
• Skin scraping: Examined under a microscope to confirm a fungal infection.
• Blood tests: Used if the infection may have spread or to check for underlying conditions.
• Imaging: Ultrasound or other scans help find abscesses or deep tissue involvement.

Treatment

Treatment depends on the type and severity of the infection:

• Bacterial infections: Topical or oral antibiotics; abscesses may need to be drained.
• Fungal infections: Antifungal creams, powders, or, for stubborn cases, oral antifungal medicine.
• Viral infections: Antiviral medicines for some infections; many warts and mild viral rashes resolve on their own or are removed.
• Parasitic infections: Medicated creams or lotions to kill mites or lice, along with cleaning bedding and clothing.

Keeping the area clean and dry, finishing the full course of any prescribed medicine, and watching for spreading or worsening symptoms all support healing. Serious or deep infections may require intravenous antibiotics in a hospital.

Prevention

• Wash hands regularly and keep skin clean
• Clean and cover cuts, scrapes, and wounds until they heal
• Keep skin dry, especially in folds and between toes
• Avoid sharing towels, razors, and other personal items
• Manage conditions such as diabetes and eczema
• Treat athlete's foot and other minor infections promptly so they do not spread

When to See a Doctor

See a doctor if a skin infection is spreading, not improving with self-care, or accompanied by fever. Seek prompt or emergency care if you have:

• Rapidly spreading redness, swelling, or red streaks from the area
• Severe pain that seems out of proportion to the skin's appearance
• High fever, chills, confusion, or a fast heartbeat
• Skin that turns purple, gray, or black, or develops blisters quickly

These can signal a deep, fast-moving infection or blood infection (sepsis), which are medical emergencies. People with diabetes or weakened immune systems should seek care early.

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC). Skin Infections.
2. Mayo Clinic. Cellulitis and skin infections.
3. MedlinePlus, U.S. National Library of Medicine. Skin Infections.
4. American Academy of Dermatology. Skin infections.