Causes and Risk Factors
Most skin and nail infections are caused by dermatophytes, molds that feed on keratin in skin, hair, and nails; yeast (Candida) favors moist skin folds. Risk rises with:- Heat, sweat, and moisture: Closed shoes, damp socks, sweaty workouts, and humid weather create ideal growing conditions.
- Shared wet surfaces: Pool decks, locker rooms, communal showers, and nail salons can pass fungus from person to person.
- Diabetes: People with diabetes get fungal infections more easily and heal more slowly, making foot checks essential.
- Older age and poor circulation: Slower nail growth and conditions such as peripheral arterial disease make toenail infections harder to clear.
- A weakened immune system: Immune-suppressing illnesses and medications allow fungi to spread more aggressively.
- Close contact and pets: Ringworm spreads through wrestling and other skin-to-skin sports, and puppies, kittens, and farm animals can carry it into a household.
Symptoms
Appearance depends on the site of infection:- Athlete's foot: Itching, burning, scaling, and cracking between the toes or on the soles, per the Mayo Clinic.
- Ringworm and jock itch: An expanding, ring-shaped rash with a scaly, raised border and clearer center, on the body or groin.
- Nail fungus: Thickened, yellow or white, brittle, crumbly nails that may lift from the nail bed; toenails are affected far more often than fingernails.
- Yeast infections: Bright red, moist patches with small satellite spots in skin folds under the breasts, in the groin, or in the armpits.
- Scalp ringworm (tinea capitis): Scaly, itchy patches with broken hairs or small bald spots, seen mainly in children and always requiring oral medication because creams cannot reach the hair root.
- Tinea versicolor: Flat, finely scaling spots on the chest, back, and shoulders that stay lighter or darker than surrounding skin and become most obvious after sun exposure.
Diagnosis
Many infections are recognized on examination, but appearances can deceive. Because eczema and dermatitis can look similar, your clinician may confirm the diagnosis with a simple skin scraping examined under the microscope or a nail clipping sent for testing — an important step before committing to months of oral therapy. Thickened, discolored nails are especially worth confirming, since repeated shoe trauma, psoriasis, and poor circulation all produce nails that look fungal but will not improve with antifungal medication.Treatment
Treatment matches the site and severity of infection:- Topical antifungals: Creams such as clotrimazole or terbinafine, used daily for two to four weeks, clear most skin infections.
- Oral antifungals: Nail infections and widespread or stubborn skin infections usually need oral terbinafine or fluconazole for weeks to months, with occasional lab monitoring.
- Moisture control: Drying thoroughly after bathing, changing socks often, alternating shoes, using antifungal powder, and wearing sandals in communal showers prevent reinfection.
- Treating every affected site at once: Clearing athlete's foot while ignoring infected toenails — or the reverse — almost guarantees the infection returns, so treat skin and nails together and dust shoes with antifungal powder.