Skin Infection: Signs, Causes and What to Do

How to tell if your skin is infected

Some redness and swelling are part of normal healing, especially in the first 48 hours. Infection is more likely when symptoms get worse rather than better after the first couple of days.

Mark it: draw around the edge of the redness with a pen and note the time. If redness moves past the line within hours, get medical care.

On darker skin, redness can be harder to see. Infected skin may look darker brown, purple or gray, and warmth, swelling, pain and shine are better guides.

What it could be

Infected wound

A cut, scrape, burn, surgical wound or piercing that becomes red, painful and oozes pus. See wound infection.

Cellulitis

Cellulitis is a bacterial infection of the deeper skin layers. It causes a spreading, red, warm, swollen and tender area, usually on a leg, often without a visible wound. Fever is common. It needs antibiotics.

Boils and abscesses

A boil is an infected hair follicle that forms a painful, red lump with a white or yellow head. An abscess is a larger pocket of pus. Both are often caused by Staphylococcus aureus, including MRSA. Larger ones need drainage.

Impetigo

Impetigo causes honey-colored crusts, often around the nose and mouth of children. It is highly contagious and is treated with antibiotic cream or tablets.

Infected eczema or bites

Scratching itchy skin lets bacteria in. Weeping, yellow crusts and sudden worsening of eczema or insect bites suggest infection. Painful clustered blisters on eczema can be eczema herpeticum, a herpes infection that needs urgent care.

Fungal infections

Ringworm, athlete's foot and jock itch cause red, itchy, scaly rings or patches that spread slowly. They are not hot or very painful, and they do not respond to antibiotics. They can crack the skin and let bacteria in.

Serious deep infections

Necrotizing fasciitis is rare but life-threatening. Warning signs are severe pain greater than the skin's appearance suggests, rapid spread, dusky or blistered skin, and feeling very ill.

For an overview of all infection types, see skin infections.

Who is at higher risk

• People with diabetes, especially foot wounds
• Weakened immune systems (chemotherapy, steroids, HIV)
• Poor circulation, leg swelling or lymphedema
• Eczema, athlete's foot or other skin breaks
• Recent surgery, bites or injecting drugs
• Contact sports, crowded living conditions and shared razors or towels (MRSA spread)

What to do for a possibly infected cut or skin area

1. Wash gently with soap and running water once or twice a day.
2. Cover with a clean, non-stick dressing and change it daily or when wet.
3. Raise an infected arm or leg to reduce swelling.
4. Warm compresses for 10 to 15 minutes several times a day help a small boil come to a head and drain.
5. Do not squeeze boils or pimples, especially on the face.
6. Pain relief: acetaminophen (paracetamol) or ibuprofen at the label dose.
7. Mark and watch the edge of the redness.

Over-the-counter antibiotic ointments have limited benefit for established infection and can cause allergic rashes. They are not a substitute for medical care when an infection is spreading.

Medical treatment

A doctor will examine the area, check temperature and pulse, and may take a swab of pus. Treatment may include:

• Incision and drainage for abscesses and large boils, which is often the main treatment
• Oral antibiotics for cellulitis, infected wounds and bites, chosen to cover strep and staph, and MRSA when likely
• Intravenous antibiotics in the hospital for severe or rapidly spreading infection
• Antifungal creams for fungal infections
• Tetanus booster if not up to date

Improvement should begin within 48 to 72 hours of antibiotics. Redness can take a week or two to fade completely.

Frequently asked questions

How do I know if my skin infection is serious?

It is serious if redness is spreading quickly or past a pen line, you see red streaks, you have a fever or chills, the pain is severe or out of proportion, or the skin turns dark, blistered or numb. These need same-day or emergency care.

What does an infected cut look like?

An infected cut becomes redder, more swollen, warm and painful after the first 2 days instead of improving. It may ooze cloudy, yellow or green pus, smell bad, or develop a spreading red area. Normal healing shows a thin pink edge and less pain each day.

Can a skin infection go away on its own?

Small boils and very mild wound infections sometimes resolve with warm compresses and good wound care. Spreading infections like cellulitis need antibiotics, and abscesses usually need drainage. Do not wait if redness is spreading or you develop a fever.

Should I put antibiotic ointment on an infected cut?

Ointment may help prevent infection in a minor clean cut, but it does little for an established infection and can cause allergic reactions. Keep the wound clean and covered. If redness spreads or pus forms, see a doctor for assessment and possible oral antibiotics.

Is a skin infection contagious?

Some are. Impetigo, MRSA boils, ringworm and scabies spread through skin contact and shared items like towels and razors. Cellulitis itself is not usually contagious. Cover wounds, wash hands and do not share personal items.