Fingernail fungus is caused by microscopic fungi that break through the nail’s protective layers and feed on keratin, the protein that makes nails hard. About 5.5% of people worldwide have a fungal nail infection at any given time, and while toenails are affected far more often, fingernails are particularly vulnerable to a type of yeast called Candida. Several factors determine whether your nails stay clear or become infected, from how often your hands are wet to how well your immune system functions.
The Organisms Behind Nail Fungus
Three categories of fungi cause nail infections, and which one you’re dealing with depends partly on whether the infection is on your fingers or toes. Dermatophytes, a group of fungi that specialize in breaking down keratin, account for 80% to 90% of all fungal nail infections. They’re the dominant cause of toenail fungus and can affect fingernails too.
Fingernails, however, are more commonly infected by Candida species, a type of yeast that also causes oral thrush and vaginal yeast infections. Candida thrives in warm, moist environments and tends to target nails that are frequently exposed to water. A smaller percentage of infections, roughly 2% to 10%, come from environmental molds found in soil and decaying plant material.
How Fungi Get Into the Nail
Fungal infections typically start at the edge where the nail meets the skin underneath, then work inward. The fungi attach to the underside of the nail plate, which is softer and more porous than the top surface. Once attached, they produce enzymes that dissolve the bonds between nail cells, creating gaps and pores in the tissue. This enzymatic breakdown is what eventually makes infected nails crumbly and brittle.
As the infection progresses, fungal threads (called hyphae) push deeper into the nail plate while spores cling to newly roughened surfaces. The nail bed reacts to the invasion by producing extra keratin, which is why infected nails thicken over time. If the infection reaches the nail matrix, the growth center at the base of the nail, it can cause permanent structural damage. At that point, nails may grow in abnormally thick, misshapen, or fragile even after the fungus is treated.
Moisture and Repeated Hand Exposure
Your hands encounter water, chemicals, and potential contaminants far more than you might realize, and that constant exposure is one of the biggest risk factors for fingernail fungus specifically. People who work with their hands submerged in water regularly, such as dishwashers, bartenders, cleaners, and healthcare workers, are especially prone to Candida infections. Prolonged moisture softens the seal between the nail and the surrounding skin, giving yeast an entry point.
Wearing gloves that trap sweat creates a similar problem. The warm, damp environment inside rubber or latex gloves is ideal for fungal growth, particularly during long shifts. If you wear gloves for work, cotton liners can help absorb moisture and reduce risk.
Nail Damage and Salon Equipment
Any injury to the nail, even a minor one, can open a pathway for fungi. Aggressive manicures that push back or cut the cuticle too forcefully remove a natural barrier against infection. Biting or picking at nails creates tiny breaks in the skin fold around the nail, and those small wounds are enough for Candida to establish itself.
Nail salon equipment is another transmission route. OSHA notes that workers and clients can be exposed to fungal infections through tools that haven’t been properly cleaned between uses. Metal implements like cuticle pushers, nippers, and nail files can carry fungal spores from one person to the next. If a salon doesn’t visibly sterilize tools or use disposable implements, the risk goes up.
Health Conditions That Raise Your Risk
Diabetes is one of the strongest risk factors for fungal nail infections, and it creates vulnerability through multiple pathways at once. Elevated blood sugar provides fungi with a nutrient-rich environment to grow in. At the same time, diabetes often reduces blood flow to the extremities, which means fewer immune cells reach the fingers and toes to fight off early infections. People with diabetic nerve damage may also miss the early signs of infection because they’ve lost sensation in their fingertips.
Any condition or medication that suppresses the immune system increases susceptibility. People with HIV, those taking immunosuppressive drugs after organ transplants, or those on long-term corticosteroids are all at higher risk. In people with chronic immune deficiencies, Candida infections can become persistent and severe, causing nails to thicken, crack, and discolor repeatedly. Poor circulation from any cause, not just diabetes, also plays a role by slowing the body’s ability to deliver immune defenses to the nail bed.
How to Tell It’s Fungus and Not Something Else
Nail psoriasis is the condition most commonly confused with fungal infection, but the two look different once you know what to spot. Fungal infections on fingernails usually affect one or two nails at a time and cause yellowing, thickening, and crumbling that starts at the nail’s free edge. Psoriasis tends to affect multiple fingernails simultaneously and produces small pits or divots on the nail surface, shallow depressions that don’t go all the way through.
Psoriasis also causes a distinctive “oil spot” discoloration, a yellowish-brown patch visible through the nail plate, which doesn’t occur with fungal infections. Another telling sign: psoriasis of the nails almost always appears alongside psoriasis elsewhere on the body, such as scaly patches on the elbows, knees, or scalp. A single discolored fingernail with no other skin symptoms points more toward fungus or trauma.
Nail trauma from repeated impact or a single injury can also mimic fungal infection. A bruised or damaged nail may turn dark, lift from the bed, or thicken as it grows out. The key difference is that trauma-related changes typically grow out with the nail over several months, while fungal infections persist or worsen without treatment. If you’re uncertain, a doctor can take a small clipping and test it for fungal organisms to confirm the diagnosis before starting treatment.
Why Fingernails Are Easier to Treat Than Toenails
If there’s a silver lining to fingernail fungus, it’s that fingernails respond to treatment faster than toenails. Fingernails grow about three times faster than toenails, which means antifungal medications can reach the infection site more quickly and a healthy nail replaces the damaged one sooner. Most fingernail infections clear within three to six months of treatment, compared to a year or longer for toenails.
Topical antifungal treatments applied directly to the nail tend to work better on fingers than toes for the same reason: faster growth means the medication cycles through more quickly. For deeper infections that have reached the nail matrix, oral antifungal treatment is typically more effective, as it reaches the infection through the bloodstream rather than trying to penetrate the nail from the outside.