Fungal Infections: Symptoms, Types & Treatment

What Are Fungal Infections?

Fungal infections (mycoses) are caused by microscopic fungi that invade the skin, nails, or mucous membranes. The two main types are yeast infections (caused by Candida species) and dermatophyte infections (caused by mold-like fungi). These infections are extremely common, affecting 20-25% of the global population, and while usually not serious, they can cause significant discomfort and spread if untreated.

Fungi are organisms that exist everywhere in our environment, including on the human body. Under normal circumstances, the body's immune system and the balance of microorganisms living on the skin prevent these fungi from causing problems. However, when conditions favor fungal growth, or when the body's defenses are weakened, these organisms can multiply rapidly and cause infection.

The risk of developing fungal infections is higher in certain populations, including infants under one year of age, pregnant women, older adults, and people with compromised immune systems. Understanding the different types of fungal infections, their causes, and available treatments empowers individuals to recognize symptoms early and seek appropriate care.

Fungal infections can affect virtually any part of the body, but they most commonly occur in areas that are warm and moist, such as between the toes, in the groin, under the breasts, and in the mouth or genital area. The appearance and symptoms of a fungal infection depend largely on where on the body it occurs and which type of fungus is responsible.

Types of Fungi That Cause Infections

Two main categories of fungi are responsible for the majority of superficial fungal infections. Understanding these categories helps in recognizing symptoms and selecting appropriate treatment.

Yeasts are single-celled fungi that normally live on the skin and mucous membranes without causing problems. The most common disease-causing yeast is Candida, which can cause infections in the mouth (thrush), genitals (yeast infection), and skin folds. Another yeast, Malassezia, is responsible for conditions like seborrheic dermatitis (dandruff) and pityriasis versicolor (a condition causing discolored skin patches).

Dermatophytes are mold-like fungi that feed on keratin, the protein found in skin, hair, and nails. Unlike yeasts, dermatophytes are not normal inhabitants of the body - they are acquired from the environment, other people, or animals. Dermatophyte infections are collectively called "tinea" and include athlete's foot (tinea pedis), jock itch (tinea cruris), ringworm (tinea corporis), and nail fungus (tinea unguium or onychomycosis).

What Causes Yeast Infections?

Yeast infections occur when Candida or Malassezia fungi, which normally live harmlessly on the body, overgrow due to disrupted balance. Common triggers include antibiotic use, weakened immunity, hormonal changes, diabetes, and wearing occlusive clothing. The infections typically affect the mouth, genitals, and skin folds.

Yeast fungi exist naturally in the mouth, vagina, intestines, and sebaceous glands without causing any symptoms. These organisms are part of the normal microbiome and typically coexist peacefully with bacteria and other microorganisms on the body. Problems arise when the delicate balance of these microorganisms is disrupted, allowing yeasts to proliferate unchecked.

Several factors can disrupt this balance and promote yeast overgrowth. Antibiotic treatment is one of the most common triggers, as antibiotics kill beneficial bacteria that normally keep yeast populations in check. Immunosuppression from illness, medications, or conditions like HIV/AIDS reduces the body's ability to control fungal growth. Hormonal changes during pregnancy, menstruation, or from oral contraceptive use can alter the vaginal environment and promote yeast growth.

Diabetes is a significant risk factor for yeast infections because elevated blood sugar provides an abundant food source for fungi. Additionally, diabetes impairs immune function and blood circulation, making it harder for the body to fight infections. People who wear dentures are at increased risk of oral thrush, as the moist environment under dentures creates ideal conditions for yeast growth.

Common Candida Infections

Vaginal yeast infections (vulvovaginal candidiasis) are extremely common, with approximately 75% of women experiencing at least one during their lifetime. Symptoms include intense itching, irritation, redness, and a thick, white, odorless discharge often described as resembling cottage cheese. The infection can also affect the external genital area (vulva), causing swelling and discomfort.

Thrush (oral candidiasis) manifests as creamy white patches on the tongue, inner cheeks, roof of the mouth, and throat. These patches may be painful and can bleed slightly when scraped. Thrush is most common in infants, who often recover without treatment, but it can also affect adults, particularly those with weakened immune systems, diabetes, or those taking inhaled corticosteroids for asthma.

Candidal balanitis affects the head of the penis and foreskin in men. Symptoms include redness, itching, white patches, and sometimes a discharge. This condition is more common in uncircumcised men and those with diabetes.

Malassezia-Related Conditions

Seborrheic dermatitis (dandruff or cradle cap in infants) is caused by an overgrowth of Malassezia yeast in areas rich in sebaceous glands. It appears as scaly, flaky patches on the scalp, eyebrows, sides of the nose, behind the ears, and on the chest. The condition is chronic and tends to flare up periodically, especially during stress or cold weather.

Pityriasis versicolor (tinea versicolor) causes patches of skin that are lighter or darker than the surrounding skin. These patches most commonly appear on the trunk, shoulders, and upper arms - areas with abundant sebaceous glands. The condition is more noticeable after sun exposure, as the affected skin doesn't tan normally.

What Causes Dermatophyte Infections?

Dermatophyte infections (tinea) are caused by mold-like fungi that don't normally live on human skin. They spread through direct contact with infected people, animals, or contaminated surfaces like shower floors and gym equipment. Common types include athlete's foot, ringworm, jock itch, and nail fungus.

Unlike yeasts, dermatophytes are not part of the normal human microbiome. These fungi must be acquired from external sources, making dermatophyte infections truly contagious. The fungi feed on keratin, the protein that forms the outer layer of skin, hair, and nails, which explains why these are the primary sites of infection.

Dermatophytes can spread through direct skin-to-skin contact with an infected person or animal. Cats, dogs, and other pets can harbor dermatophytes and transmit them to humans, particularly certain species of ringworm. Contact with contaminated objects or surfaces - known as fomites - is another important transmission route. Shower floors, locker room benches, towels, and shared shoes are common sources of infection, particularly for athlete's foot.

The warm, humid environment inside shoes creates ideal conditions for fungal growth, which is why athlete's foot is so prevalent. Once the fungi establish themselves between the toes, they can spread to other parts of the foot, the groin (via contaminated towels or underwear), or other body areas.

Athlete's Foot (Tinea Pedis)

Athlete's foot is the most common dermatophyte infection, affecting up to 15% of the adult population. The infection typically begins between the toes, where skin becomes red, itchy, cracked, and may peel or blister. A burning or stinging sensation is common, especially when the area becomes wet.

The infection often spreads from between the toes to the sole and sides of the foot. In the "moccasin" pattern, the entire sole becomes dry, thickened, and scaly, resembling the leather of a moccasin shoe. This chronic form can be more resistant to treatment and often coexists with nail fungus.

Athlete's foot is rare in children under 10 years of age. The infection spreads easily in communal areas where people go barefoot, such as swimming pools, gyms, and locker rooms. Wearing occlusive, non-breathable footwear and allowing feet to remain sweaty increases the risk of developing and maintaining the infection.

Jock Itch (Tinea Cruris)

Jock itch affects the groin, inner thighs, and sometimes the buttocks. It appears as a red, raised, scaly rash with well-defined borders that may form a ring pattern. The rash is intensely itchy and may burn, especially during physical activity when the area becomes warm and sweaty.

This infection is more common in men than women and frequently occurs alongside athlete's foot, as the fungi can spread from the feet to the groin via hands or towels. Tight-fitting underwear and athletic supporters that trap moisture increase the risk of jock itch.

Ringworm (Tinea Corporis)

Despite its name, ringworm has nothing to do with worms - it's named for its characteristic ring-shaped appearance. The infection appears as circular or oval patches with a raised, red, scaly border and clearer skin in the center. Multiple rings may appear and can overlap, creating irregular patterns.

Ringworm can occur anywhere on the body and is often acquired from infected pets, particularly cats and dogs. Children are more frequently affected than adults. The patches are usually itchy and can spread to other parts of the body or to other people through direct contact.

Scalp Ringworm (Tinea Capitis)

Scalp ringworm primarily affects children and appears as scaly patches on the scalp that may resemble severe dandruff. Unlike seborrheic dermatitis, scalp ringworm causes hair loss in the affected areas, leaving bald patches. The infection can cause brittle hair that breaks off at the scalp surface, appearing as black dots.

In some cases, a severe inflammatory reaction called a kerion can develop - a painful, boggy mass on the scalp that may ooze pus and cause permanent scarring and hair loss. Scalp ringworm requires oral antifungal treatment, as topical medications cannot penetrate the hair follicles effectively.

Nail Fungus (Onychomycosis)

Nail fungus most commonly affects the toenails and typically begins at the tip of the nail, gradually spreading toward the nail base. The infected nail becomes thickened, discolored (yellow, brown, or white), and brittle. The nail may separate from the nail bed and develop a crumbly texture.

Nail fungus is challenging to treat because the fungi reside within the nail plate, protected from topical medications. Complete resolution requires growing an entirely new, healthy nail, which takes 6-12 months for fingernails and 12-18 months for toenails. Nail fungus often coexists with athlete's foot and can serve as a reservoir for recurrent foot infections.

What Are the Symptoms of Fungal Infections?

Fungal infections cause symptoms that vary by location. Skin infections typically cause redness, itching, scaling, and sometimes blisters or cracking. Mucous membrane infections cause redness, white patches, and burning. Nail infections cause discoloration, thickening, and brittleness. Symptoms can sometimes mimic other skin conditions.

The symptoms of fungal infections depend primarily on which part of the body is affected and which type of fungus is responsible. However, some general patterns are common across most fungal infections. Understanding these symptoms helps in recognizing when a fungal infection might be present and when medical consultation is warranted.

Fungal infections can sometimes be difficult to distinguish from other skin conditions such as eczema, psoriasis, or bacterial infections. A healthcare provider can often make the diagnosis based on the appearance and distribution of the rash, but laboratory tests may be needed in some cases to confirm the diagnosis and identify the specific fungus involved.

Skin Symptoms

Fungal infections of the skin typically cause redness in the affected area, ranging from mild pinkness to intense, angry redness. Itching is almost universal and can range from mild to severe and maddening. The affected skin often develops scaling or flaking, with the dead skin peeling off in small or large flakes.

In some cases, the skin may crack or fissure, particularly between the toes or in skin folds. These cracks can be painful and may provide an entry point for bacterial infections. Blisters may develop, especially with acute athlete's foot, and can be filled with clear fluid. In chronic infections, the skin may become thickened and leathery.

Mucous Membrane Symptoms

Fungal infections of mucous membranes, such as the mouth or vagina, have somewhat different symptoms. In the mouth, thrush causes white, creamy patches that may be painful and can bleed when scraped. The underlying tissue is typically bright red and may appear raw. Burning or soreness is common, and eating or drinking may be uncomfortable.

Vaginal yeast infections cause intense itching and irritation of the vagina and vulva. A thick, white discharge with a cottage cheese-like consistency is characteristic, though the discharge has no odor. Redness and swelling of the vulva are common, and there may be burning during urination or intercourse.

Nail Symptoms

Nail fungus causes progressive changes in the appearance of the affected nails. Early signs include white or yellow spots or streaks under the tip of the nail. As the infection advances, the nail becomes thickened and may become difficult to trim. The nail plate takes on a yellowish, brownish, or opaque appearance.

The texture of the nail changes, becoming brittle, crumbly, or ragged. The nail may separate from the nail bed (onycholysis), and debris may accumulate under the nail, further distorting its shape. In severe cases, the nail may become so thickened and distorted that it causes pain when wearing shoes.

When Should You See a Doctor for a Fungal Infection?

Seek medical care if over-the-counter treatment hasn't worked after 2-4 weeks, if the infection is spreading or worsening, if you have diabetes or a weakened immune system, if you notice signs of bacterial infection (pus, fever, increasing pain), or if you have scalp ringworm or nail fungus.

Many fungal infections can be successfully treated at home with over-the-counter antifungal medications. However, there are circumstances where professional medical evaluation and prescription treatment are necessary for proper resolution of the infection.

If you've been using an over-the-counter antifungal product for several weeks without improvement, it's time to consult a healthcare provider. The infection may be caused by a resistant fungus, may require a stronger medication, or may not actually be a fungal infection at all - some skin conditions can mimic fungal infections and require different treatment.

People with diabetes should seek medical attention promptly for any fungal infection, as these individuals are at higher risk of complications, including bacterial superinfection and poor wound healing. Similarly, anyone with a weakened immune system - whether from HIV/AIDS, cancer treatment, organ transplantation, or immunosuppressive medications - should consult a healthcare provider, as fungal infections can become serious in these populations.

How Are Fungal Infections Treated?

Fungal infections are treated with antifungal medications in topical form (creams, sprays, shampoos) for skin infections or oral form for nail and scalp infections. Treatment duration varies: 2-4 weeks for most skin infections, 6-12 weeks of oral medication for nail fungus. Keeping the affected area clean and dry is essential.

The cornerstone of fungal infection treatment is antifungal medication, which kills the fungi or prevents their growth. The choice between topical and oral medications depends on the location and severity of the infection, as well as the patient's overall health status. In addition to medication, environmental measures to reduce moisture and prevent reinfection are crucial for treatment success.

Because fungi thrive in warm, moist environments, keeping the affected areas clean and dry is an essential component of treatment. This means thoroughly drying between toes after bathing, wearing breathable fabrics, changing socks if feet become sweaty, and avoiding occlusive footwear when possible.

Over-the-Counter Treatments

Many fungal infections can be effectively treated with medications available without a prescription. These topical antifungals come in various forms including creams, ointments, gels, sprays, powders, and solutions. Common active ingredients include clotrimazole, miconazole, terbinafine, and tolnaftate.

For athlete's foot and jock itch, apply the antifungal medication to the affected area and surrounding skin twice daily. Continue treatment for at least 2 weeks after symptoms resolve to prevent recurrence - this typically means 3-4 weeks of total treatment. Using antifungal powder in shoes and on feet can help prevent reinfection.

Vaginal yeast infections can be treated with over-the-counter antifungal suppositories, creams, or tablets that are inserted into the vagina. Treatment regimens range from 1-day to 7-day courses. For external symptoms, antifungal cream can be applied to the vulva. If symptoms persist or the infection recurs frequently, medical evaluation is recommended.

Seborrheic dermatitis (dandruff) responds well to medicated shampoos containing antifungal ingredients such as ketoconazole, selenium sulfide, or zinc pyrithione. These shampoos are used several times per week initially, then less frequently for maintenance.

Prescription Treatments

Some fungal infections require prescription-strength medications, either because over-the-counter treatments aren't strong enough or because the infection location requires oral medication that can reach the fungi from within the body.

Nail fungus is almost always treated with oral antifungal medications because topical treatments cannot penetrate the nail plate effectively. Prescription nail lacquer (amorolphine or ciclopirox) can be used for mild cases, but oral medications such as terbinafine or itraconazole are more effective. Treatment typically lasts 6-12 weeks, but complete clearing requires growing an entirely new nail, which takes 6-12 months for fingernails and 12-18 months for toenails.

Scalp ringworm always requires oral antifungal treatment because topical medications cannot penetrate the hair follicles. Griseofulvin has been the traditional treatment, but terbinafine and itraconazole are increasingly used. Treatment typically lasts 4-8 weeks. Using an antifungal shampoo alongside oral medication may help reduce spread to others.

Severe or widespread skin infections may also require oral antifungal medication, particularly if they haven't responded to topical treatment or if the patient has a weakened immune system. Prescription-strength topical antifungals may be used for stubborn infections.

Treatment for Pregnancy and Breastfeeding

Many antifungal medications are safe to use during pregnancy and breastfeeding, but it's important to consult with a healthcare provider before starting any treatment. Topical antifungal creams are generally considered safe when used as directed, as they are minimally absorbed into the bloodstream.

Oral antifungal medications should be avoided during pregnancy unless absolutely necessary, as some carry risks to the developing fetus. Healthcare providers can help weigh the risks and benefits and recommend the safest treatment option.

What Are Serious Invasive Fungal Infections?

Invasive fungal infections occur when fungi enter deep tissues and internal organs like the lungs, bloodstream, or brain. These rare but serious infections primarily affect people with severely weakened immune systems. Symptoms include persistent fever and depend on which organ is affected. Prompt diagnosis and intravenous antifungal treatment are essential.

While the fungal infections discussed thus far affect the skin, nails, and mucous membranes, fungi can sometimes invade deeper tissues and organs. These invasive fungal infections are uncommon in the general population but represent a significant threat to people with severely compromised immune systems.

Risk factors for invasive fungal infections include severe immunocompromise from conditions like HIV/AIDS, cancer (especially blood cancers like leukemia), or treatments that suppress the immune system such as chemotherapy, organ transplant medications, or high-dose corticosteroids. Other risk factors include extended stays in intensive care units, burns, major surgical procedures, and kidney dialysis.

Invasive fungal infections can affect many different organs, including the lungs, bloodstream, urinary tract, heart, and even the brain. The symptoms depend on which organ is involved but commonly include persistent fever that doesn't respond to antibiotics. Other symptoms may be vague and nonspecific, making diagnosis challenging.

Treatment of invasive fungal infections requires intravenous antifungal medications and typically prolonged courses of therapy. The prognosis depends on the specific fungus involved, the patient's underlying health status, and how quickly treatment is initiated. Prevention through careful hygiene and, in some cases, prophylactic antifungal medications is an important strategy for high-risk individuals.

How Can You Prevent Fungal Infections?

Prevent fungal infections by keeping skin clean and dry, especially between toes and in skin folds. Wear breathable fabrics and change sweaty socks. Use sandals in public showers and gyms. Don't share towels, shoes, or personal items. Treat athlete's foot promptly to prevent spread to nails.

Prevention of fungal infections focuses on creating an environment hostile to fungal growth - one that is clean, dry, and well-ventilated. Because many fungal infections spread from person to person or through contaminated surfaces, avoiding exposure is also important.

For preventing athlete's foot and other dermatophyte infections:

• Dry feet thoroughly after bathing, especially between toes
• Wear sandals or flip-flops in public showers, locker rooms, and around swimming pools
• Choose shoes made of breathable materials and allow shoes to dry completely between wearings
• Change socks if they become sweaty; moisture-wicking socks can help
• Don't share shoes, socks, towels, or personal items
• Treat athlete's foot promptly to prevent spread to nails and other body areas

For preventing yeast infections:

• Wear cotton underwear and avoid tight-fitting pants or pantyhose
• Change out of wet swimsuits and sweaty workout clothes promptly
• Avoid unnecessary antibiotic use (discuss with your doctor)
• For denture wearers: remove dentures at night and clean them regularly
• Manage diabetes well to reduce blood sugar levels
• Avoid douching, which disrupts the natural vaginal flora