Toenail fungus is a common infection that can cause a nail to become discolored, thick, brittle or misshapen. The condition, medically known as onychomycosis, is more common in toenails than fingernails and can take months to clear with treatment.
The infection occurs when fungi grow in or beneath the nail. Small cracks in the nail or surrounding skin can allow fungi to enter, while warm, damp environments such as public showers, swimming pools and locker rooms can provide conditions where fungi thrive.
What causes toenail fungus?
Several types of fungi can cause nail infections. Dermatophytes are the most common, although yeasts and molds can also infect nails. Athlete’s foot, another fungal infection, can spread from the skin of the foot to the toenails.
The risk is higher for people who regularly have sweaty feet, wear shoes that keep their feet damp, walk barefoot in wet public areas or have previously had athlete’s foot. Older age, nail injuries, psoriasis, diabetes, poor blood flow and a weakened immune system can also increase the risk.
Being overweight or stressed, however, should not be presented as established causes of toenail fungus. The available medical guidance identifies other risk factors, including moisture, previous fungal infections, nail injury and certain medical conditions.
Is toenail fungus contagious?
Yes. Fungal nail infections can spread between people through direct contact and through contaminated items such as towels or nail clippers. They can also be picked up from contaminated surfaces in places such as public showers, pools and locker rooms.
A person can also spread the infection from one part of the body to another. Athlete’s foot, for example, can spread to the toenails.
Keeping the feet clean and dry, changing socks regularly, wearing footwear in communal showers and keeping nail tools clean can reduce the risk of infection and reinfection.
What does toenail fungus look like?
An infected nail may develop white, yellow, brown or other discoloration. It can become thick, brittle, cracked or misshapen, and may lift away from the nail bed. In more severe cases, the nail can become painful and make walking or standing difficult.
Not every discolored or damaged nail has a fungal infection. Nail injuries, psoriasis and other conditions can produce similar changes. For that reason, a health care provider may examine the nail and, when necessary, take a nail clipping or sample from beneath the nail for laboratory testing.
How is toenail fungus treated?
Treatment depends on the extent of the infection and the type of fungus involved. Mild cases may be treated with medicines applied directly to the nail, while more extensive infections may require prescription antifungal medication taken by mouth.
Prescription topical treatments include medicines such as efinaconazole and tavaborole. They are applied to the affected nail over an extended period, and improvement can take months because toenails grow slowly.
For some patients, an oral antifungal such as terbinafine or itraconazole may be prescribed. These medicines can have side effects and interact with other medicines, so a health care provider may assess a patient’s medical history and, in some cases, check liver function before or during treatment.
The American Academy of Dermatology recommends confirming a suspected fungal infection before starting oral antifungal treatment because other nail conditions can look similar to fungus.
Removing part or all of an affected nail may sometimes be considered, particularly when the infection is severe or medication needs better access to the infected area. Permanent surgical removal of the nail is used less often.
Why does treatment take so long?
Treating the fungus and restoring the appearance of the nail are separate processes. Even when medication clears the infection, the damaged portion of the nail must grow out before the nail looks normal again.
The American Academy of Dermatology says treatment with oral terbinafine for toenail fungus typically lasts about 12 weeks, while the nail may take a year or longer to completely grow out.
Fungal nail infections can also return after successful treatment, making prevention and follow-up important.
Who should seek medical care?
People with diabetes or a weakened immune system should seek medical advice if they suspect a fungal nail infection because foot problems can pose greater risks in these groups. Medical attention is also appropriate when a nail becomes increasingly painful, swollen, discolored or misshapen, or when the infection is spreading to other nails.
A health care provider can determine whether the nail changes are caused by fungus or another condition and recommend treatment based on the diagnosis.
Preventing toenail fungus
Keeping feet dry and nails trimmed can help lower the risk. Health authorities also recommend changing socks regularly, wearing shoes that allow the feet to breathe and using footwear in communal showers and pool areas. Nail clippers and other tools should not be shared and should be properly cleaned.
Treating athlete’s foot promptly can also help prevent the infection from reaching the nails.
Toenail fungus is treatable, but recovery can take time. Because several nail conditions can look similar, an accurate diagnosis is important before choosing treatment.
