Fungal Infection

Overview

A fungal infection, also called a mycosis, develops when fungi invade and multiply in the body. Fungi are a normal part of the environment and even live on and inside the body in small numbers. Problems arise when they overgrow or enter tissue where they do not belong.

Most fungal infections affect the surface of the body, such as the skin, nails, mouth, or genitals, and are mild and treatable. Common examples include athlete's foot, ringworm, nail fungus, and yeast infections. Less commonly, fungi can cause deeper or widespread infections, which tend to be more serious and usually affect people with weakened immune systems.

Symptoms

Symptoms depend on which part of the body is affected:

• Skin infections: Red, scaly, itchy patches, sometimes with a ring-shaped rash (ringworm), cracking and peeling between the toes (athlete's foot), or rashes in warm, moist skin folds.
• Nail infections: Thickened, discolored, brittle, or crumbling nails.
• Mouth and throat (oral thrush): White patches on the tongue and inner cheeks, soreness, and difficulty swallowing.
• Vaginal yeast infections: Itching, irritation, and a thick discharge.
• Deep or systemic infections: Fever, cough, fatigue, and other symptoms depending on the organs involved.

Surface infections are usually itchy and uncomfortable rather than dangerous, while deeper infections can cause more serious, body-wide symptoms.

Causes

Fungal infections are caused by different types of fungi, including:

• Dermatophytes, which feed on keratin in skin, hair, and nails and cause ringworm, athlete's foot, and jock itch.
• Yeasts such as Candida, which normally live on the body but can overgrow to cause thrush, vaginal yeast infections, and skin-fold rashes.
• Molds and environmental fungi, which can cause deeper infections when their spores are inhaled or enter through a wound.

Fungi thrive in warm, moist environments. Many spread through direct skin contact, contact with contaminated surfaces such as locker room floors, or sharing items like towels, shoes, and personal grooming tools.

Risk Factors

Several factors make fungal infections more likely:

• Warm, moist skin, from sweating, tight footwear, or prolonged dampness.
• A weakened immune system, from conditions such as diabetes, HIV, cancer treatment, or use of medicines that suppress immunity.
• Recent antibiotic use, which can upset the natural balance of microbes and allow yeast to overgrow.
• Close-contact environments, such as gyms, pools, and communal showers.
• Poor circulation and breaks in the skin that let fungi enter.

Diagnosis

Many surface fungal infections can be recognized by their appearance during a physical examination. To confirm the diagnosis or identify the specific fungus, a clinician may:

• Take a scraping of skin, a nail clipping, or a swab to examine under a microscope.
• Send a sample to a laboratory for culture, which can identify the exact fungus but takes time.
• Use a special ultraviolet lamp for certain skin infections.

For suspected deep or internal fungal infections, blood tests, imaging, and tissue samples may be needed. Confirming the type of fungus helps guide the most effective treatment, especially for stubborn or recurring infections.

Treatment

Treatment depends on the location and severity of the infection:

• Topical antifungals: Creams, powders, sprays, and shampoos treat many skin and scalp infections and mild yeast infections.
• Oral antifungals: Pills are used for nail infections, widespread or stubborn skin infections, and oral thrush, and they often require several weeks or months for nail infections.
• Antifungal lozenges or rinses for oral thrush.
• Intravenous antifungal medicines in a hospital for serious deep or systemic infections.

It is important to complete the full course of treatment even after symptoms improve, because stopping early can allow the infection to return. Keeping the affected area clean and dry supports healing.

Prevention

Many fungal infections can be prevented with good hygiene and by keeping skin dry:

• Keep skin clean and dry, especially between the toes and in skin folds.
• Wear breathable footwear and clean, dry socks, and change them when damp.
• Wear flip-flops or sandals in public showers, locker rooms, and around pools.
• Do not share towels, shoes, socks, or grooming tools.
• Manage underlying conditions such as diabetes, and use cotton or moisture-wicking clothing.

When to See a Doctor

See a healthcare provider if:

• A rash or nail change does not improve with over-the-counter antifungal products.
• The infection spreads, recurs frequently, or is widespread.
• You have diabetes or a weakened immune system, since infections can be more serious and harder to treat.
• You develop signs of a spreading bacterial infection, such as increasing redness, warmth, swelling, pus, or fever.

Seek prompt care for symptoms of a possible deep or internal fungal infection, such as persistent fever, cough, or fatigue, particularly if your immune system is weakened, as these infections can be serious and need specialized treatment.

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC). Fungal Diseases.
2. Mayo Clinic. Fungal infections.
3. MedlinePlus, U.S. National Library of Medicine.
4. American Academy of Dermatology.