Severe Athlete’s Foot: Symptoms, Risk Factors, Treatment

Athlete’s foot, also called tinea pedis, is a common fungal skin infection that is often considered a nuisance but one that can turn serious for some people. Severe athlete's foot may be caused by different strains of the fungus and/or because a person has a weakened immune system. Diabetes, poor foot hygiene, and undertreatment of the infection can add to the risk.

When athlete's foot turns severe, it can move beyond the toes and involve the entire foot or cause itchy blisters (vesicles) or pitted sores (ulcers).

This article describes the symptoms and causes of severe athlete's foot, including the risk factors and possible complications. It also explains how severe athlete's foot is diagnosed and treated and when to see a healthcare provider.

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Close up of athlete's foot

Reproduced with permission from © DermNet and © Raimo Suhonen www.dermnetnz.org 2023.

Symptoms of Severe Athlete’s Foot

Athlete's foot commonly affects the spaces between the toes, a condition referred to as interdigital athlete's foot. Symptoms may be mild and sometimes barely recognizable. At other times, the symptoms will be more overt and cause:

  • Itchiness, particularly when your socks and shoes are removed
  • Scaling, peeling, or cracking between the toes
  • Reddened or darkened skin
  • Burning or stinging

When the condition turns severe it can cause:

  • Dry, scaly, or cracking skin covering the entire bottom of the foot and creeping up the side
  • Soft, saturated areas of skin between the toes (maceration) caused by the breakdown of tissues
  • Clusters of tiny blisters, often on top of the toes and the arch and inner sole of the foot
  • Painful ulcers, often on the ball of the foot and the heel

Athlete's foot is highly contagious and can be spread through direct contact with infected skin or indirect contact with contaminated items (such as clothing or towels) or surfaces (such as locker room floors or shower stalls).

Types of Athlete’s Foot

Interdigital athlete's foot is the milder and more common form of the disease mainly caused by the fungus Trichophyton rubrum. The infection is often self-limiting, resolving on its own in 30% to 40% of cases. Other cases are easily treated with over-the-counter antifungals.

But, there are two other subtypes that can cause more severe symptoms and be less likely to resolve without extensive treatment. These are largely regarded as severe athlete's foot.

Plantar Athlete’s Foot

Plantar athlete's foot, also known as chronic scaly athlete's foot or "mocassin foot," is also mainly caused by Trichophyton rubrum. But, for reasons that are not always clear, the fungus can move from the toes to cover the entire sole of the foot and, in some cases, the sides and back of the heel.

Plantar athlete’s foot cause fine, dry, silvery scales and the progressive thickening of the skin of the sole. Over time, the skin can crack and peel, exposing red, raw skin.

The infection can even sometimes spread to the hand with scratching and then to the opposite foot. The usual pattern of infection is two feet and one hand, or one foot and two hands. Less commonly, this infection can spread to other areas of the body.

Acute Vesicular Athlete's Foot

This is the least common type of athlete’s foot, often caused by a fungus called Trichophyton mentagrophytes. It typically starts with an interdigital infection that fails to respond to standard antifungal therapy and progressively gets worse.

One of the contributing factors to this type of infection is persistently moist feet. Historically, it was known as “jungle rot” as it affected soldiers fighting in moist, tropical conditions.

Acute vesicular athlete’s foot is characterized by the sudden outbreak of painful blisters on the sole or top of the foot. The initial outbreak can be followed by recurrent episodes that become progressively worse, leading to the formation of painful foot ulcers.

A severe form of vesicular athlete's foot is called acute vesiculobullous athlete's foot because it causes larger blisters (bullae) that can burst and form pitted, painful ulcers.

Vesicular athlete's foot can occasionally leap to other parts of the body, including the arms, chest, or sides of the fingers. These secondary blisters are caused by an allergic reaction to the fungus, called an id reaction.

Risk Factors for Severe Athlete's Foot

Athlete's foot can affect anyone, but there are several risk factors that can predispose you to the infection including:

  • Sharing footwear
  • Walking barefoot in a public locker room or shower
  • Wearing shoes or socks for prolonged periods
  • Having sweaty feet

Risk factors for severe athlete's foot include:

  • Having diabetes which reduces blood flow to the foot, making it harder to fight infections
  • Having a compromised immune system, such as people with untreated HIV
  • Being on immunosuppressive drugs, such as those used to prevent organ transplant rejection or treat autoimmune diseases
  • Living in an area where Trichophyton mentagrophytes is common, such as parts of Europe, Asia, and India

Athlete’s foot affects about 15% of adults and is more common in males than females.

How Is Severe Athlete’s Foot Diagnosed?

Athlete’s foot can often be diagnosed with a physical examination alone. Laboratory tests may be used to rule out other possible causes or identify the specific fungal strain (particularly when a severe infection does not respond to standard treatments).

Physical Exam

For the physical exam, your healthcare provider will ask you about your symptoms, how long you've had them, and whether you have predisposing factors. Your healthcare provider will then visually inspect your feet, as well as other areas of your skin.

KOH Test

You might also have a KOH test. This is a painless procedure in which a skin scraping is taken from scales, a rash, or a blister for rapid testing.

A positive KOH test confirms the presence of skin-associated fungi (referred to as a dermatophyte). A negative KOH test does not rule out athlete’s foot as the fungi can be difficult to isolate, particularly with interdigital athlete’s foot.

Fungal Culture

A fungal culture is a more specific test in which the scraping is sent to the lab to physically "grow" the fungus. This culture takes several days to grow but can identify the specific type and strain of dermatophyte.

If another cause of your foot symptoms is suspected—such as a bacterial infection, poison ivy, or vascular disease—you may undergo additional testing.

How Athlete's Foot Is Treated

Even severe athlete's foot can be cured with the right treatment plan. It will ultimately involve medical treatment along with some lifestyle adjustments.

The treatment plan may include:

  • Improved foot hygiene: Wash your feet twice daily and, gently dry between the toes with a fresh towel. Launder the towel to prevent the spread of the infection.
  • Over-the-counter topical antifungals: These are applied as an ointment, gel, cream, lotion, powder, or spray to the affected skin, usually twice daily for two to four weeks. Options include Lotrimin (clotrimazole) and Tinactin (tolnaftate).
  • Oral antifungals: These prescription drugs are used when topical antifungals fail. These are taken by mouth for two to six months. Options include terbinafine and itraconazole. Because oral antifungals can affect the liver, regular blood tests are needed to monitor liver function.

Home remedies, such as washing your feet in a vinegar solution, can also be helpful when used along with antifungal medication but are not curative.

How to Prevent Severe Athlete’s Foot

Even if you have predisposing factors for athlete's foot, there are things you can do to effectively avoid getting infected:

  • Keep your feet clean, dry, and cool.
  • Avoid public swimming pools, showers, saunas, spas, jacuzzis, or shared foot baths.
  • If you use showers and locker rooms at a gym, wear sandals.
  • Allow shoes to air out by alternating them every two to three days.
  • If your feet are prone to sweatiness, use foot antiperspirant.
  • Change socks at least once daily. If your socks become sweaty in the middle of the day, remove them as soon as you can.
  • Avoid socks made from fabrics that don’t dry easily, such as nylon.
  • Instead of closed shoes, wear flip-flops, sandals, and open-toe shoes whenever possible.

Complications if Left Untreated

The main complication of severe athlete's foot is a secondary bacterial infection. This occurs when the fungal infection causes a break in the skin that allows bacteria easy access to the underlying tissues. Common bacterial agents include Staphylococcal aureus and Streptococcus pyogenes, both of which reside on the skin.

A secondary bacterial infection can lead to a potentially serious superficial infection called cellulitis. On rare occasions, the infection can spread to the bloodstream and trigger a potentially life-threatening reaction known as sepsis.

A less serious but potentially more persistent complication is a fungal nail infection (onychomycosis). Also known as tinea unguium, the infections are notoriously difficult to treat and can lead to cracking, pitting, discoloration, and the eventual shedding of the nail from the nail bed.

When to See a Healthcare Provider

The first rule of thumb is to see a healthcare provider when athlete's foot fails to respond to over-the-counter antifungals after four weeks of consistent use.

Seek immediate medical treatment if there are signs of severe bacterial infection, including:

  • High fever with shaking chills
  • Areas of severe redness, warmth, swelling, and pain
  • A foul-smelling discharge from a break in the skin
  • Inability to walk on the affected foot
  • Expanding redness or red streaks from the affected area (a sign of cellulitis)

Summary

Severe athlete's foot can occur if the fungal infection involves more than the toes and fails to respond to standard antifungal treatment. This includes plantar athlete's foot (a.k.a. "mocassin shoe") which involves the entire sole of the foot and acute vesicular athlete's foot which causes painful blisters and sores on the foot.

Risk factors for severe athlete's foot include diabetes, having a compromised immune system, and failing to treat (or failing to respond to) antifungal therapy. The treatment of severe athlete's foot may require lifestyle changes and oral antifungals like itraconazole and terbinafine.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Ilkit M, Durdu M. Tinea pedis: The etiology and global epidemiology of a common fungal infection. Crit Rev Microbiol. 2015;41(3):374-88. doi:10.3109/1040841X.2013.856853

  2. Ward H, Parkes N, Smith C, Kluzek S, Pearson R. Consensus for the treatment of tinea pedis: a systematic review of randomised controlled trials. J Fungi (Basel). 2022 Apr;8(4):351. doi:10.3390/jof8040351

  3. Kong QT, Du X, Yang R, Huang SY, Sang H, Liu WD. Chronically recurrent and widespread tinea corporis due to Trichophyton rubrum in an immunocompetent patient. Mycopathologia. 2015 Apr;179(3-4):293-7. doi:10.1007/s11046-014-9834-5

  4. Newland JG, Abdel-Rahman SM. Update on terbinafine with a focus on dermatophytosesClin Cosmet Investig Dermatol. 2009;2:49–63. Published 2009 Apr 21. doi:10.2147/ccid.s3690

  5. Lestner J, Hope WW. Itraconazole: an update on pharmacology and clinical use for treatment of invasive and allergic fungal infections. Expert Opin Drug Metab Toxicol. 2013 Jul;9(7):911-26. doi:10.1517/17425255.2013.794785

  6. Kara Polat A, Akın Belli A, Göre Karaali M, Koku Aksu AE. The attitudes, behaviors, and opinions about non-pharmacological agents in patients with tinea pedis. Dermatol Ther. 2020 Nov;33(6):e14041. doi:10.1111/dth.14041

  7. Karaman BF, Topal SG, Aksungur VL, Ünal İ, İlkit M. Successive potassium hydroxide testing for improved diagnosis of tinea pedis. Cutis. 2017 Aug;100(2):110-114. PMID: 28961287.

  8. Centers for Disease Control and Prevention. Hygiene related diseases: athlete's foot (tinea pedis).

  9. Jimenez-Garcia L, Celis-Aguilar E, Díaz-Pavón G, et al. Efficacy of topical clotrimazole vs. topical tolnaftate in the treatment of otomycosis. A randomized controlled clinical trial. Braz J Otorhinolaryngol. 2020 May-Jun;86(3):300-307. doi:10.1016/j.bjorl.2018.12.007

By Heather L. Brannon, MD
Heather L. Brannon, MD, is a family practice physician in Mauldin, South Carolina. She has been in practice for over 20 years.