Fungi are a diverse group of organisms found in nearly every environment, including on and within the human body. While many fungi are harmless, or even beneficial, certain types can cause infections when conditions are right. These infections can range from superficial skin issues to more serious internal conditions. Understanding these organisms helps in recognizing, treating, and preventing fungal infections.
Fungi and the Human Body
Fungi are eukaryotic organisms. On the human body, fungi commonly reside on the skin, nails, and mucous membranes, forming part of the body’s natural microbiome. Some species, like Candida albicans, are commensal, meaning they live in or on us without causing harm and can even be beneficial.
Under specific conditions, these commensal fungi can become pathogenic, leading to an infection. Factors such as a weakened immune system, prolonged antibiotic use disrupting the balance of other microbes, or environments with excessive moisture can trigger an overgrowth or shift in fungal populations.
Common Fungal Infections
Dermatophyte Infections
Dermatophyte infections, often referred to as ringworm or tinea, are common fungal infections affecting the skin, hair, and nails. These infections are caused by molds like Trichophyton, Microsporum, and Epidermophyton species, which feed on keratin, a protein found in the outer layer of skin, hair, and nails. Symptoms include red, itchy, scaly patches that can be circular, sometimes with a raised border.
Specific Dermatophyte Types
Athlete’s foot (tinea pedis) presents with scaling, itching, and fissuring between the toes, and is acquired in warm, moist environments like public showers. Jock itch (tinea cruris) affects the groin area, causing burning and itching, linked to high temperature and humidity, or tight clothing. Ringworm on the scalp (tinea capitis) can lead to hair loss, redness, scaling, and pus-filled lesions.
Yeast Infections
Yeast infections are primarily caused by Candida species. Candida albicans is a common cause, naturally present on the skin, mouth, and vagina.
Oral thrush, or candidiasis, appears as white patches in the mouth and throat, accompanied by soreness, a cotton-like feeling, and difficulty swallowing. Vaginal yeast infections cause itching, soreness, vulvar redness, and a thick, white, cottage cheese-like discharge. These infections can arise from antibiotic use, changes in hormone levels, or a compromised immune system. Candida can also cause rashes in skin folds, appearing as bright red, itchy patches with small pustules at the edges.
Nail Fungus (Onychomycosis)
Nail fungus, known as onychomycosis or tinea unguium, is a fungal infection of the nails, most commonly affecting toenails. The infected nail becomes thickened, discolored (white or yellow), brittle, and crumbly. As the infection progresses, the nail may separate from the nail bed and can emit an unpleasant odor.
Risk factors include:
- Older age
- Excessive sweating
- Previous athlete’s foot
- Walking barefoot in damp public areas
- Minor nail injury
- Underlying conditions like diabetes or impaired circulation
Diagnosis and Treatment of Fungal Infections
Healthcare professionals diagnose fungal infections through a combination of methods. A physical examination and discussion of symptoms provide initial clues, especially for visible skin infections. For definitive diagnosis, a skin scraping, hair sample, or nail clipping may be taken and examined under a microscope using a potassium hydroxide (KOH) wet mount to look for fungal elements. Sometimes, a fungal culture may be performed to grow and identify the specific type of fungus causing the infection, which can be particularly useful for scalp or nail infections. For more widespread or internal infections, blood tests or biopsies of affected tissues may be necessary.
Treatment Approaches
Treatment approaches vary depending on the type and severity of the fungal infection. Superficial infections of the skin and nails are treated with topical antifungal medications, available as creams, gels, ointments, sprays, or powders. These medications work by killing the fungus or inhibiting its growth. Common topical antifungals include clotrimazole, econazole, and terbinafine.
For more extensive, severe, or persistent infections, oral antifungal medications may be prescribed. These systemic treatments are taken by mouth and circulate throughout the body to reach the infection site. It is important to complete the full course of treatment as prescribed, even if symptoms improve, to prevent the fungus from returning.
Preventing Fungal Infections
Preventing fungal infections involves maintaining good hygiene and managing environmental conditions that favor fungal growth. Regular washing of the skin with soap and water, followed by thorough drying, especially in skin folds, between toes, and other moist areas, reduces risk. Fungi thrive in warm, damp environments, so keeping skin dry is a primary defense.
Wearing breathable fabrics and changing socks regularly, particularly if feet sweat heavily, helps to absorb moisture and allow air circulation. In public areas like showers, locker rooms, or swimming pools, wearing appropriate footwear can prevent direct contact with contaminated surfaces. Avoiding the sharing of personal items like towels, shoes, and clothing also reduces the spread of fungal spores. Managing underlying health conditions can also reduce susceptibility to fungal infections.