Foot Infections: Types, Signs and Treatment

Why feet get infected

Feet spend hours in warm, damp, dark shoes, which suits fungi and bacteria. Small cracks, blisters, cut cuticles and ingrown nails give germs a way in. Infection risk rises with:

• sweaty feet and tight, non-breathable footwear
• walking barefoot in locker rooms, pools and showers
• diabetes, peripheral artery disease and nerve damage
• older age, smoking and a weakened immune system
• swelling (lymphedema or chronic leg edema)

Untreated athlete's foot is a common entry point for cellulitis, because the cracked skin between the toes lets bacteria in.

Types of foot infection compared

Fungal foot infections

Athlete's foot

Athlete's foot (tinea pedis) causes itching, burning and white, soggy, peeling skin between the toes, especially the fourth and fifth. A "moccasin" type causes dry, fine scaling over the sole and sides. Over-the-counter terbinafine, clotrimazole or miconazole cream works in most cases. Continue for 1 to 2 weeks after the skin looks clear.

Toenail fungus

Fungal nail infection usually starts at the tip of the nail and spreads back, making it thick, discolored and brittle. It is often painless but can make shoes uncomfortable. A nail clipping test confirms it, because psoriasis and nail trauma look similar. Oral terbinafine is most effective but takes 3 months, and nails take 12 to 18 months to grow out clear. Topical lacquers work for mild cases.

Bacterial foot infections

Cellulitis

Cellulitis is a spreading infection of the deeper skin layers. The foot or lower leg becomes red, warm, swollen and tender, often with a poorly defined edge. Fever and swollen glands in the groin can follow. It usually starts from cracked skin, athlete's foot, a wound or an insect bite. Most cases respond to oral antibiotics. Marking the edge of the redness with a pen helps show whether it is spreading.

Infected ingrown toenail

The edge of the nail grows into the side of the toe, usually the big toe, causing pain, redness and swelling and then pus. Warm soaks help early cases. Recurrent or infected ingrown nails often need partial nail removal. See ingrown toenail infection and surgery and paronychia.

Puncture wounds

Stepping on a nail or glass can carry bacteria deep into the foot. A nail through a sneaker sole can introduce Pseudomonas, which can infect bone or cartilage. Pain that gets worse after a few days is a warning sign. See puncture wound for first aid and tetanus advice.

Deep infections

Untreated or high-risk infections can spread to bone (osteomyelitis), joints (septic arthritis) or along tendon sheaths. These need imaging, sometimes surgery, and weeks of antibiotics.

Viral foot infections

Plantar warts are caused by HPV picked up from damp floors. They are pushed inward by walking, so they form hard, painful spots, interrupting the skin lines and showing tiny black dots (clotted capillaries). Many clear on their own within 1 to 2 years. Salicylic acid and freezing speed this up. Do not try to cut them out yourself.

Foot infections and diabetes

Diabetes changes the rules. Nerve damage can hide pain, poor circulation slows healing, and infections can reach bone before anyone notices. Any red, warm or draining wound in a person with diabetes needs same-day assessment. Read more about diabetic foot infection.

How foot infections are diagnosed

Most are diagnosed by looking at the foot. Your doctor may also:

• scrape skin or clip a nail for fungal microscopy and culture
• swab pus to identify bacteria and check for MRSA
• take an X-ray to look for a foreign body, gas or bone damage
• order an MRI if bone infection is suspected
• check blood sugar, pulses and sensation in the feet

Preventing foot infections

• Dry thoroughly between the toes after washing.
• Wear moisture-wicking socks and change them daily, or more often if your feet sweat.
• Rotate shoes so each pair dries for 24 hours.
• Wear sandals in communal showers, pools and gyms.
• Cut toenails straight across and not too short.
• Treat athlete's foot early to protect the skin barrier.
• If you have diabetes, check your feet daily and never walk barefoot.

Frequently asked questions

How do I know if my foot infection is bacterial or fungal?

Fungal infections usually itch and peel, develop slowly and do not cause fever or spreading redness. Bacterial infections cause warmth, swelling, throbbing pain, pus and redness that spreads, sometimes with fever. The two often occur together, since cracked skin from athlete's foot can let bacteria in.

When should I see a doctor for a foot infection?

See a doctor for spreading redness, pus, increasing pain, red streaks, fever, or any infection if you have diabetes, poor circulation or weak immunity. Also see one if athlete's foot does not clear after 2 to 4 weeks of over-the-counter treatment.

Can a foot infection spread to the rest of the body?

Yes. Bacterial infections can spread into the leg as cellulitis, into bone as osteomyelitis, or into the bloodstream, causing sepsis. Fever, chills, confusion or rapidly spreading redness need emergency care.

What is the best home treatment for an infected toe?

For a mildly red, sore toe without spreading redness, soak it in warm water for 15 minutes 2 to 3 times a day, keep it clean and dry, and wear open or roomy shoes. If there is pus, spreading redness, or no improvement in 2 to 3 days, see a doctor for antibiotics or drainage.

Are foot infections contagious?

Athlete's foot, nail fungus and plantar warts spread on damp floors, towels and shared shoes. Bacterial cellulitis is not usually contagious, although MRSA from draining wounds can spread through contact. Cover wounds and do not share towels or footwear.