Skin on Leg or Foot Looks Infected

Signs that skin is infected

Bacterial skin infection causes inflammation, so the classic signs are:

• redness that may look pink, red, purple or dark brown depending on skin tone
• warmth compared with the other leg
• swelling and tightness
• pain or tenderness
• pus, yellow crust or cloudy, smelly discharge from a wound
• red streaks spreading up the leg (lymphangitis)
• fever, chills or feeling unwell

One leg affected suggests infection. Both legs equally red is much more likely to be something else, such as stasis dermatitis, because cellulitis rarely affects both legs at once.

Common causes

Cellulitis

Cellulitis is an infection of the deeper layers of skin, usually by streptococcus or staphylococcus bacteria. The lower leg is the most common site. Bacteria enter through a break in the skin: a cut, insect bite, cracked heel, athlete's foot or swollen skin. It causes a spreading area of redness, warmth and swelling with poorly defined edges, often with fever. Risk factors include leg swelling, obesity, diabetes, previous cellulitis and lymphedema.

Erysipelas is a more superficial form with a raised, sharply defined, bright red edge.

Infected wounds, blisters and bites

A cut, graze, surgical wound, blister or insect bite becomes infected when redness spreads beyond the edges, pain increases after day 2 or 3, or pus appears. Wound infection is more likely with dirty wounds, puncture wounds and bites.

Infected ingrown toenail

The nail edge pierces the skin at the side of the toe, usually the big toe. The fold becomes red, swollen and tender, with pus or overgrown tissue. It often follows cutting nails too short or curved, or tight shoes.

Diabetic foot infection

In people with diabetes, nerve damage means injuries go unnoticed, and poor circulation slows healing. An ulcer on the sole or toes can become infected with little pain. Warning signs are new redness around an ulcer, swelling, a bad smell, drainage, or blood sugar rising for no other reason. A diabetic foot infection can spread to bone (osteomyelitis) and is a leading cause of amputation, so it needs prompt care.

Abscesses and boils

A boil is an infected hair follicle; an abscess is a larger collection of pus. They form a painful, fluctuant (squishy) lump and often need draining. MRSA is a frequent cause.

Athlete's foot and fungal infection

Athlete's foot causes itchy, peeling, cracked skin between the toes. It is not usually a bacterial infection itself, but the cracks are a common entry point for cellulitis.

Look-alikes that are not infection

How doctors assess it

A clinician will look at the skin, check temperature, pulse and blood pressure, feel for an abscess, check pulses and sensation in the foot, and ask about diabetes, wounds and previous episodes. Many draw a line around the redness to track spread. Tests may include:

• blood tests for white cell count and inflammation if you are unwell
• a swab of pus or ulcer tissue
• X-ray or MRI for possible bone infection under a foot ulcer
• ultrasound to find an abscess or exclude a DVT

Treatment

• Antibiotics: most uncomplicated cellulitis is treated with antibiotic tablets for about 5 to 7 days. IV antibiotics are used for severe infection, fever with signs of sepsis or failure to improve.
• Drainage: abscesses need to be opened and drained. Antibiotics alone are not enough.
• Raise the leg above heart level as much as possible for the first few days. This reduces swelling and speeds recovery.
• Treat the entry point: athlete's foot, cracked heels, ingrown toenails and leg swelling, to prevent recurrence.
• Diabetic foot infections: antibiotics, wound cleaning, removal of dead tissue, offloading pressure from the ulcer and checking circulation, ideally by a specialist foot team.
• Pain relief: acetaminophen (paracetamol) or ibuprofen, following the label dose.

Redness may look slightly worse in the first 24 to 48 hours of antibiotics. After that, it should steadily fade. If it keeps spreading, or fever persists, seek review.

Preventing leg and foot infections

• Clean cuts and scrapes with soap and water and cover them.
• Moisturize dry, cracked heels and treat athlete's foot promptly.
• Control leg swelling with raising the legs and compression stockings if advised.
• If you have diabetes, check your feet every day, never walk barefoot, and see a podiatrist regularly.
• Cut toenails straight across.

Frequently asked questions

How do I know if the skin on my leg is infected?

Infected skin is usually red or darkened, warm, swollen and increasingly painful, and may ooze pus or show red streaks. Fever and chills suggest the infection is spreading. Redness only at a wound's edge in the first day or two is often normal healing.

What does cellulitis on the lower leg look like?

Lower leg cellulitis looks like a swollen, warm, tender patch of red, pink or darker skin with blurred edges, usually on one leg. It may spread over hours and come with fever. The skin can look shiny or dimpled like orange peel, and blisters sometimes form.

When should I worry about a foot infection?

Get same-day care for spreading redness, fever, red streaks, pus or any foot infection if you have diabetes or poor circulation. Go to the ER for severe pain, skin turning dark or blistering, or signs of sepsis such as confusion and a racing heart.

Can a leg infection go away on its own?

A very mild infection at the edge of a small cut sometimes settles with cleaning. Cellulitis, abscesses and infected ulcers usually need antibiotics or drainage, and untreated infections can spread to the blood or bone. Do not wait if redness is spreading.

Why are both of my lower legs red?

Redness of both lower legs is rarely cellulitis. It is more often stasis dermatitis from poor vein circulation, eczema or a reaction to compression stockings or creams. It still deserves a check, but it usually needs skin care and swelling control rather than antibiotics.