Skin on Arm or Hand Looks Infected: What to Do

How to tell if the skin is infected

Normal healing causes some redness, mild swelling and tenderness for 2 to 3 days. Infection is likely when:

• redness spreads beyond the edge of the wound, or keeps growing
• the area becomes hotter, more swollen and more painful after day 2 or 3
• yellow, green or cloudy pus drains, or there is a bad smell
• red streaks run up the arm toward the armpit
• you develop fever, chills or swollen, tender lymph nodes in the elbow or armpit

Tip: draw around the edge of the redness with a pen and note the time. If it spreads beyond the line, get seen.

Common causes

Cellulitis

Cellulitis is a spreading infection of the deeper skin layers. The area is red, warm, swollen and tender, with a poorly defined edge. It often starts from a small break in the skin such as a scratch, insect bite, eczema or a cracked cuticle. Erysipelas, a more superficial form, has a raised, sharply defined edge.

Abscess

An abscess is a pocket of pus under the skin. It feels like a firm, painful lump that softens and may come to a head. MRSA commonly causes abscesses, sometimes mistaken for a spider bite. Most need to be drained.

Infected wounds

Cuts, scrapes, splinters, burns and surgical wounds can become infected, especially if dirt remains in the wound. See wound infection.

Hand-specific infections

• Paronychia: red, swollen, painful skin around the side or base of a nail, often after nail biting, hangnails or manicures. Pus may collect under the skin.
• Felon: a tense, throbbing infection of the fingertip pad, often after a puncture. It needs drainage.
• Flexor tenosynovitis: infection in the tendon sheath of a finger. The finger is swollen, held bent and very painful to straighten. It is a surgical emergency.
• Herpetic whitlow: clusters of small blisters on a fingertip from herpes virus. It should not be cut open.

Bites

• Animal bites: cat bites cause deep punctures with a high infection risk, often within 12 to 24 hours.
• Human bites and "fight bites": a knuckle cut from a punch to the mouth can carry mouth bacteria into the joint and is a high-risk injury.

Lymphangitis

Red streaks tracking up the arm mean infection is spreading through the lymph vessels. See lymphangitis. It needs antibiotics promptly.

Look-alikes

Not every red, swollen area is infected. Allergic reactions to bites, contact dermatitis, gout in the hand or wrist, blood clots in arm veins, and IV line irritation can look similar. These usually itch, or lack fever and pus.

Who is at higher risk

• people with diabetes, especially if blood sugar is poorly controlled
• weakened immunity from medicines, cancer treatment or HIV
• lymphedema of the arm, for example after breast cancer surgery
• IV drug use
• eczema or cracked skin on the hands
• jobs with frequent cuts or wet hands, such as fishing, food prep, healthcare and gardening

How doctors diagnose it

Diagnosis is usually based on the appearance and history. A doctor may:

• mark the edge of redness to track spread
• swab pus for culture to guide antibiotics, especially if MRSA is suspected
• use ultrasound to find a hidden abscess
• order blood tests if you are unwell, and X-rays for bites, foreign bodies or deep infections

Treatment

• Cellulitis: oral antibiotics for 5 to 10 days. Improvement should start within 48 hours, though redness may look worse in the first day. IV antibiotics are used for severe infection or if you are unwell.
• Abscess: incision and drainage is the main treatment; antibiotics are added in some cases.
• Paronychia: warm soaks for 15 minutes 3 to 4 times a day; drainage if pus collects; antibiotics if spreading.
• Bites: cleaning, often preventive antibiotics, and checking tetanus and, if relevant, rabies risk.
• Deep hand infections: urgent surgical washout by a hand surgeon plus IV antibiotics.
• Necrotizing fasciitis: emergency surgery and IV antibiotics.

Home care while healing

• Keep the arm or hand raised above heart level to reduce swelling.
• Keep wounds clean and covered; change dressings daily.
• Take all antibiotics as prescribed, even if it looks better.
• Use acetaminophen (paracetamol) or ibuprofen for pain, following the label dose.
• Return if redness spreads past your pen line, fever develops, or you are not improving after 48 to 72 hours.

How serious can a skin infection get?

Most arm and hand infections clear completely with treatment. Untreated or fast-moving infections can spread into the blood and cause sepsis, which can lead to intensive care admission. Infections of the scalp, face, hands and any wound in someone who is frail or immunocompromised can progress quickly, which is why early treatment matters.

Frequently asked questions

How do I know if a cut on my hand is infected?

Signs include redness that spreads beyond the cut, increasing warmth, swelling and pain after the first 2 to 3 days, pus, a bad smell, red streaks up the arm, or fever. Mild redness right at the edge that is shrinking is usually normal healing.

What does a red streak from a wound mean?

A red line spreading from a wound toward your armpit means infection is traveling through the lymph vessels (lymphangitis). It needs antibiotics the same day. With fever or feeling very unwell, go to the ER, because it can lead to sepsis.

Can a skin infection on the arm go away on its own?

A very mild infection at the edge of a small cut may settle with cleaning and care. Cellulitis, abscesses and infections that are spreading rarely clear without treatment and can become serious. If redness is spreading or you have a fever, see a doctor.

Why are hand infections more serious?

The hand has tight compartments, tendons and joints close to the skin. Infection can spread along tendon sheaths and into joints quickly, causing stiffness or permanent loss of function. A swollen finger that hurts to straighten, a fight bite or a cat bite needs urgent care.

How long does cellulitis on the arm take to heal?

With antibiotics, pain and fever usually improve within 2 to 3 days, and redness fades over 7 to 10 days. Some swelling and discoloration can last a few weeks. Keep the arm raised and finish the antibiotic course.