🍄 Fungal Infections: Types of Mycoses, Causes, Symptoms, and Prevention Methods

Fungal infections, or mycoses, are among the most common groups of diseases worldwide. According to medical statistics, one in five people worldwide has experienced some form of fungal infection of the skin, nails, or mucous membranes at least once in their lifetime. Despite seeming harmless, mycoses can significantly impair quality of life and, if left untreated, lead to serious complications. Fungi constitute a distinct kingdom of living organisms and are fundamentally different from both bacteria and viruses. Unlike bacteria, fungal cells have a nucleus and a complex internal structure. Unlike viruses, fungi can exist and reproduce independently, without a host cell. These characteristics make fungal infections persistent and require a prolonged, targeted approach to treatment. Understanding the nature of fungal diseases, routes of transmission, and preventive measures is an important step toward protecting the health of the skin and nails.

Types of Fungal Infections

Fungal diseases in humans are extremely diverse. They are classified according to the type of pathogen and the area affected.

Dermatophytoses

Dermatophytes are a group of fungi that feed on keratin, the protein that makes up the skin, hair, and nails. Dermatophytoses include athlete’s foot (tinea pedis), ringworm of the body (tinea corporis), jock itch (tinea cruris), ringworm of the scalp (tinea capitis), and onychomycosis—a fungal infection of the nail plates. Dermatophytes are the most common causes of fungal infections in temperate climates.

Onychomycosis (Nail Fungus)

Onychomycosis deserves special attention because it is one of the most common and persistent forms of mycosis. Fungal infections affect the toenails much more often than the fingernails—up to 80% of all cases involve the toenails. This is because the feet are more often kept in a warm, moist environment inside closed shoes, while circulation in the toes is poorer than in the fingers, slowing the immune response.

Candidiasis

Candidiasis is caused by yeast-like fungi of the genus Candida, which are normally present on the skin and mucous membranes of healthy people. When immunity is weakened, antibiotics are taken, or hormonal changes occur, Candida begins to multiply rapidly, causing inflammation. Candidiasis can affect the mouth (thrush), skin folds, nail folds, and other areas.

Tinea Versicolor

Tinea versicolor (pityriasis versicolor) is caused by the fungus Malassezia, which is also part of the skin’s normal microflora. With excessive sweating and certain characteristics of skin oils, the fungus becomes pathogenic and causes patches of various colors—from white to brown—to appear on the skin of the chest, back, shoulders, and neck. The disease is not contagious in the usual sense but tends to recur.

Nail Fungus: Stages and Signs

Onychomycosis develops gradually, progressing through several stages, each with characteristic visual signs.

Early Stage

In the early stages, the fungus causes barely noticeable changes: slight clouding of the nail plate and the appearance of white or yellowish spots and streaks near the free edge of the nail. The nail may lose some of its natural shine. At this stage, many people overlook the problem, mistaking the changes for the effects of an injury or a cosmetic defect. Treatment is most effective at this early stage and may be limited to topical medications.

Stage of Pronounced Changes

As the infection progresses, the nail plate thickens and becomes loose and brittle. Its color changes to yellow, brown, or grayish green. Keratinized material accumulates under the nail, a condition known as subungual hyperkeratosis. The nail may become deformed, and its edges begin to crumble. An unpleasant odor develops. At this stage, the fungus often spreads to neighboring nails.

Advanced Stage

Without treatment, the nail plate is completely destroyed: it separates from the nail bed (onycholysis), develops a bumpy, uneven surface, and breaks off easily. The skin around the nail becomes inflamed, and cracks and weeping areas may develop. At this stage, the fungus often affects all the toenails and may spread to the skin and fingernails. Treating advanced onychomycosis requires systemic therapy and takes anywhere from several months to a year.

Causes and Risk Factors

Fungal infections of the skin and nails develop when pathogenic fungi reach the body’s surface under conditions favorable to their reproduction. Key risk factors include:

• Visiting humid public places—swimming pools, saunas, public baths, and gym showers. Warm, moist environments are ideal for fungi, and walking barefoot on contaminated surfaces is the main route of foot infection.
• Wearing tight, poorly ventilated footwear—synthetic materials create a greenhouse effect, maintaining the moisture and temperature in which fungi thrive. Footwear that is not allowed to dry between uses is especially hazardous.
• Excessive foot sweating (hyperhidrosis)—constant moisture softens the skin, weakening its barrier function and making it easier for fungal spores to penetrate.
• Weakened immunity—chronic diseases, immunosuppressant use, prolonged antibiotic therapy, and HIV infection significantly increase susceptibility to fungal infections.
• Diabetes mellitus—impaired circulation in the limbs and elevated glucose levels create a favorable environment for fungi. Onychomycosis is 2–3 times more common in people with diabetes.
• Age—nails grow more slowly over time, circulation in the feet deteriorates, and accumulated minor injuries make it easier for infection to penetrate. After age 60, one in three people has onychomycosis.
• Using other people’s personal hygiene items—towels, slippers, manicure tools, and socks can harbor fungal spores.
• Injuries to the nails and skin—even minor cuts, cracks, chafing, and damage to the nail plate can provide an entry point for infection.

Symptoms of Fungal Infections by Location

Feet

Athlete’s foot (tinea pedis) is the most common form of fungal infection in adults. It causes scaling, redness, and itching of the skin between the toes, especially between the fourth and fifth toes, as well as small blisters and cracks on the heels and soles. In chronic cases, the skin of the feet thickens and becomes dry and rough—this is known as the “moccasin” type. Athlete’s foot often occurs together with nail fungus: the foot serves as a reservoir of infection from which the fungus penetrates beneath the nail plate.

Nails

Onychomycosis causes changes in the color of the nail plate, including white, yellow, brown, or greenish discoloration; thickening and deformation of the nail; increased brittleness and crumbling; and separation from the nail bed. The big toe is affected most often because it bears the greatest load while walking, and its nail grows more slowly than the others. Pain occurs when footwear presses against the thickened nail.

Skin Folds

Fungal infections of the skin folds—the groin, armpits, areas beneath the breasts, and between the buttocks—cause redness with clearly defined borders, itching, skin maceration, and small cracks and erosions. The most common causative agents are Candida or dermatophytes. Contributing factors include obesity, excessive sweating, and tight clothing made from synthetic fabrics.

Scalp

Ringworm of the scalp (tinea capitis) is more common in children. It causes scaly patches with broken hairs, itching, and sometimes the formation of pus-filled crusts known as kerion. In adults, it may have subtle symptoms resembling dandruff.

How Fungal Infections Spread

Fungi spread through several main routes. Direct contact involves touching the infected skin of another person or animal; some dermatophytes are transmitted by pets. Indirect contact occurs through contaminated surfaces and objects, including locker room and shower floors, mats, shoes, towels, bed linen, manicure tools, and combs. Dermatophyte spores are extremely resistant in the environment: they remain viable on surfaces for months or even years. This means that infection can occur even in your own home if one family member is affected. Sharing towels, slippers, or scissors is a common route of transmission within families.

Self-infection, or autoinoculation, is another important mechanism: fungus from the feet is transferred by the hands to the fingernails, groin, and other parts of the body. Therefore, when treating mycosis in one area, it is important to maintain good hygiene and treat all affected areas simultaneously.

Diagnosis of Fungal Infections

Accurate diagnosis of mycosis is important for selecting effective treatment because different types of fungi respond to different medications. The main diagnostic methods include:

• Visual examination—an experienced dermatologist may suspect a fungal infection based on characteristic signs. However, visual assessment is not sufficient for an accurate diagnosis because many skin conditions, including psoriasis, eczema, and nail dystrophy, can mimic mycosis.
• Microscopy with a KOH test—a skin scraping or nail fragment is treated with potassium hydroxide (KOH), which dissolves keratin and makes fungal elements such as hyphae and spores visible under a microscope. This is a quick and accessible method that can confirm the presence of fungus within 15–30 minutes.
• Culture on nutrient media—a scraping is placed on a special medium, such as Sabouraud agar, where the fungus grows for 2–4 weeks. This method can identify the specific pathogen and determine its sensitivity to medications. Its disadvantages are the long waiting period and the possibility of false-negative results.
• Dermoscopy—examination under magnification with polarized light helps distinguish fungal infections from other dermatoses.
• Wood’s lamp examination—ultraviolet radiation of a specific wavelength causes certain types of fungi to fluoresce in a characteristic way. It is used mainly to diagnose scalp microsporia.

To obtain reliable results, the sample must be collected correctly: scrapings are taken from the active edge of the lesion, not from its center. Antifungal medications should not be applied to the affected area for 2–3 weeks before testing.

Complications Without Treatment

Many people regard fungal infections of the skin and nails as a cosmetic problem and postpone visiting a doctor. However, without treatment, mycosis progresses and can lead to serious consequences:

• Spread of the infection—the fungus spreads from one nail to neighboring nails, from the feet to the hands, and from the skin of the feet to the groin and torso. The larger the affected area, the more difficult and prolonged the treatment.
• Secondary bacterial infection—cracks and erosions in the skin caused by the fungus become entry points for bacteria. This can lead to erysipelas or cellulitis, an inflammation of the subcutaneous tissue that requires antibiotic therapy and, in severe cases, hospitalization.
• Allergic sensitization—fungal metabolic products are potent allergens. Chronic mycosis can trigger or exacerbate allergic skin diseases and bronchial asthma.
• Diabetic foot—in people with diabetes, fungal foot infections significantly increase the risk of trophic ulcers and diabetic foot syndrome, potentially progressing to gangrene.
• Psychological discomfort—deformed, discolored nails and scaly skin cause embarrassment, leading people to avoid open footwear, swimming pools, and beaches. This reduces quality of life and may result in social isolation.

Prevention of Fungal Infections

Preventing a fungal infection is much easier than treating one that has already developed. The main preventive measures include:

Foot Hygiene

Wash your feet daily with soap and dry the skin between the toes thoroughly, as fungus most often begins in the moist spaces between the toes. Use a separate towel for your feet. If you are prone to excessive sweating, use drying agents or special antifungal powders.

Footwear Care

Choose footwear made from breathable natural materials such as leather or textiles. Do not wear the same pair two days in a row; allow footwear to dry completely for at least 24 hours. Periodically treat the inside of footwear with antiseptic agents or use ultraviolet shoe dryers. Do not try on shoes in stores with bare feet; wear socks.

Precautions in Public Places

Always wear rubber slippers or flip-flops in swimming pools, saunas, public baths, fitness club showers, and hotels. Do not walk barefoot on locker room floors. After visiting such places, wash and dry your feet thoroughly. If you regularly visit a swimming pool or gym, consider using antifungal foot creams as a preventive measure.

Nail Care

Trim your nails regularly without leaving overly long free edges. Use only your own manicure tools. When visiting a manicure or pedicure salon, make sure the instruments are sterilized in an autoclave. Do not cut the cuticle too short, as it protects the nail bed from infection.

Clothing and Fabrics

Wear socks made from natural materials such as cotton or wool, or modern moisture-wicking fabrics. Change your socks daily, or twice a day if you sweat excessively. Wash socks at a temperature of at least 60°C to destroy fungal spores. Underwear should also be made from natural fabrics and should not be too tight.

When to See a Dermatologist

You should see a doctor at the first signs of a fungal infection: changes in nail color or structure, scaling or itching of the skin on the feet, or the appearance of skin patches that do not disappear within two weeks. The earlier treatment begins, the more effective and shorter it will be. Modern medicine offers a wide range of antifungal treatments, from topical lacquers and creams for early-stage infections to systemic medications for advanced cases. However, self-treatment may be ineffective or even harmful: without an accurate diagnosis, it is easy to mistake a fungal infection for another condition, while an incorrectly chosen medication may obscure the clinical picture without eliminating the infection.

The most important rule is to complete the entire course of treatment, even if the symptoms disappear. Fungal spores remain deep within the nail and skin much longer than the visible signs of infection. Stopping treatment at the first sign of improvement is the most common cause of recurrence. For onychomycosis, treatment continues until a healthy nail has grown out completely, which takes 3–6 months for fingernails and 9–12 months for toenails.

Myths About Fungal Infections

There are many misconceptions about fungal diseases that interfere with timely and appropriate treatment.

“Nail fungus will go away on its own”—no, onychomycosis never resolves without treatment. Without treatment, the infection only progresses, affecting additional nails and areas of skin. Spontaneous recovery is possible with some superficial skin mycoses in young people with strong immunity, but it does not occur in nail infections.

“Nail polish conceals and treats nail fungus”—decorative nail polish has no antifungal effect. Moreover, it creates a moist, oxygen-poor environment underneath that favors fungal growth and may accelerate the infection. Special medicated nail lacquers with antifungal ingredients do exist, but they must be prescribed by a doctor.

“Vinegar and iodine will cure nail fungus”—home remedies such as vinegar, iodine, celandine, hydrogen peroxide, and garlic have no proven antifungal efficacy against onychomycosis. They may temporarily improve the condition of the skin around the nail due to their antiseptic effects, but they do not penetrate the nail plate deeply enough to destroy the fungus. Delaying a visit to the doctor in the hope that home remedies will work allows the infection to spread.

“Only people with poor hygiene get fungal infections”—this misconception stigmatizes affected individuals and discourages them from seeking help. Fungal infections are not directly related to hygiene standards: infection can occur even in the cleanest swimming pool or gym. Risk factors such as genetic predisposition, age, underlying diseases, and the type of footwear worn are unrelated to personal cleanliness.

“If the nail does not hurt, it does not need treatment”—pain from onychomycosis develops only in the late stages, when the thickened nail presses against soft tissue. The absence of pain does not mean there is no problem: the fungus continues to destroy the nail plate and remains a constant source of infection for others.

Fungal infections are not a life sentence but diseases that can be successfully treated with the right approach. The keys to success are early diagnosis, properly selected treatment, patience, and consistent adherence to preventive measures. Caring for the health of your skin and nails begins with simple daily habits: proper hygiene, suitable footwear, attention to early changes, and prompt consultation with a specialist when they appear.