Infected Foot: Symptoms, Causes, and Treatment

An infected foot occurs when the bacteria that are normally present on the skin break the skin’s barrier and enter the bloodstream causing symptoms such as pain, swelling, warmth, and redness. The infection can result from an injury, like a cut or scrape, insect bite, ingrown toenail, or a diabetic ulcer. This article discusses the symptoms, causes, and treatments for an infected foot.

Key takeaways:

Symptoms of an infected foot

The symptoms of an infected foot vary depending on the severity of the condition. Look out for the following signs as an indication that you may have an infection:

  • Tenderness to touch or pressure
  • Pain
  • Swelling
  • Redness
  • Warmth
  • Foul smell
  • Discharge (pus)
  • Fever

Causes of an infected foot

Bacteria cause an infected foot. On the skin's surface, we have bacteria that are normally present, called normal microbiota. In the past, it was believed that microbiotas were pathogens (disease agents) or potential pathogens; however, recent studies have shown that they play a protective role for humans as long as they stay on the surface of the skin.

The skin creates a barrier that keeps the microbiota from entering the deeper tissues under the skin. If these microbiota pass through the skin's barrier and enter the tissues, they can flourish, leading to an infection.

Punctures wounds, cuts, and scrapes

Certain injuries will allow not only the skin's bacteria to pass through the barrier, they allow bacteria from the external environment to enter the deeper tissues.

For instance, a puncture wound can be from any sharp object, including a nail, knife, or a sharp tooth (animal or human). In these cases, bacteria in the environment or on the object can enter the deeper tissues, leading to infection.

When a cut or scrape opens the skin's barrier, the environment's bacteria can enter into the deep tissues causing infection.

Insect bites

Numerous kinds of insects can bite the feet, including mosquitoes, fleas, and mites, leading to itching. When you scratch at the bite, it can break the skin barrier and allow bacteria to enter the deep tissues under the skin.

There is limited data if the bacteria carried by the insects enter the deeper tissues causing infection. However, we do know that other types of organisms are carried by insects that can lead to diseases such as malaria, Lyme disease, and West Nile virus.

Ingrown toenail

With an ingrown toenail, a deviating piece of the toenail grows through the skin, allowing the microbiota to enter the deeper tissue, causing infection. The aberrant piece of nail is similar to receiving a cut or puncture wound.

Even though ingrown toenails are most often caused by improper nail cutting, they can also be caused by other factors, including tight shoes, genetics, toe deformity, trauma, increased sweating, and diabetes. Ingrown toenails can be treated by soaking and other home remedies.

Diabetic ulcer

People with diabetes have higher sugar levels in their system, which damages the nerves of the feet. In addition, the higher sugar level restricts blood flow by causing blood vessels to narrow.

The poor circulation and damaged nerves can lead to a diabetic ulcer — a deep open wound sore. These ulcers easily become infected.

People with diabetes are sometimes unaware when an ulcer develops since the damaged nerves do not alert them to the pain.

Fungal infection

Athlete's foot is a fungal infection of the foot. It forms in moist, damp, and warm areas, like the atmosphere inside the socks of an athlete.

An athlete's foot causes itching, scaling, and burning; it is most common in the spaces between the toes but also found on the top of the foot, the sole, and the heel. Usually, the itching is considerable and leads to scratching. When the foot’s skin is scratched, it causes an opening for the bacteria to go through the skin and into the deeper structures.

Onychomycosis is when a fungus infects the toenail giving it a yellow appearance with occasional white spots and a rough texture. If the abnormal toenail breaks the skin's barrier, infection can result.

Viral causes

Human papillomavirus (HPV) causes warts on the soles of the feet, called plantar warts. These warts are on the skin's outer layer and result from the virus breaking through the skin. When a person picks or scratches at the plantar wart, bacteria can pass through the skin and enter the deep tissues, leading to a bacterial infection.

An important side note is that people have different immune systems; only some people who come in contact the human papillomavirus will develop warts.

Treatment and prevention of a bacterial-infected foot

Antibiotics need to be used as soon as possible. They can be taken orally, via an intramuscular injection, or intravenously (IV). In addition, a topical antibiotic ointment or cream can help fight the infection.

Once the bacterial infection has resolved, steps can be taken to prevent reinfection by eliminating the predisposing factors.

  1. Cuts and abrasions (wound care). Clean the wound with soap and water immediately, then apply topical antibiotic ointment or cream. Hydrogen peroxide was recommended in the past, but no longer since evidence has shown it prevents wound healing.
  2. Insect bites. Once bitten by an insect, numerous over-the-counter remedies can help with the itching. If in a high-risk area for insect bites, we recommend using insect repellant.
  3. Ingrown toenail. Keep your toes properly trimmed and try to avoid tight shoes.
  4. Fungal infection. Antifungal creams can be purchased over the counter or by prescription. In addition, antifungal creams can be combined with a topical corticosteroid cream to help the itching.
  5. Toenail fungus. A toenail fungus can be treated with topical meds or oral pills.
  6. Plantar warts. Plantar warts can be treated with over-the-counter topicals or treated by a dermatologist.

An infected foot is caused by bacteria breaking the foot's skin barrier, fortunately there are multiple ways to treat and further prevent an infected foot.

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