You may first notice a fungal toenail infection as a small white or yellow spot on the tip of your toenail, especially the big toe. As the infection progresses, the toenail can become yellow, brittle—even crumbly—and thick and uneven-looking. In the worst fungal infections, the toenail separates from the nail bed. This is called onycholysis. As fungal infections worsen, the nail beds can be tender to the touch and quite painful. Sometimes women try to pretend the pain is “normal” and ignore it altogether.
Physical exam alone has been shown to be an unreliable method of diagnosing fungal nails. There are many conditions that can make nails look damaged, so even doctors have a difficult time. In fact, studies have found that only about 50% of cases of abnormal nail appearance were caused by fungus. Therefore, laboratory testing is almost always indicated. Some insurance companies may even ask for a laboratory test confirmation of the diagnosis in order for antifungal medicine to be covered. A nail sample is obtained either by clipping the toenail or by drilling a hole in the nail. That piece of nail is sent to a lab where it can by stained, cultured, or tested by PCR (to identify the genetic material of the organisms) to identify the presence of fungus. Staining and culturing can take up to six weeks to get a result, but PCR to identify the fungal genetic material, if available, can be done in about one day. However, this test is not widely used due to its high cost. If a negative biopsy result is accompanied by high clinical suspicion, such as nails that are ragged, discolored, thickened, and crumbly, it warrants a repeat test due to the prevalence of false-negative results in these tests.
Green nails can be caused by Pseudomonas bacteria, which grow under a nail that has partially separated from the nail bed. This infection may cause a foul odor of the nails. The treatment is to trim the nail short every four weeks, don't clean it, polish if you want to hide the color, and wait two to three months. It is also advised to avoid soaking the nail in any sort of water (even if inside gloves) and to thoroughly dry the nail after bathing. If the problem continues, there are prescription treatments that your doctor may try.

Occlusive shoe materials, such as vinyl, which cause the feet to remain moist, provide an excellent area for the fungus to proliferate. Likewise, absorbent socks like cotton that wick water away from your feet may help. Some individuals who sweat excessively benefit from the application of antiperspirants like 20% aluminum chloride (Drysol). Powders can help keep your feet dry. Although counterintuitive, if your feet can be soaked in a solution of aluminum acetate (Burow's solution or Domeboro solution) and then air dried with a fan, this can be very helpful if performed three or four times within 30 minutes. A home remedy of dilute white vinegar soaks, using one part vinegar and roughly four parts water, once or twice a day (as 10-minute foot soaks) may aid in treatment followed by evaporation can be helpful.
Nail infections occur more often in men than in women, and the infections are found in adults more often than in children. If you have family members who often get these types of fungal infections, you’re more likely to get them as well. Older adults are at the highest risk for getting fungal infections of the nails because they have poorer circulation and their nails grow more slowly and thicken as they age.

No one knows where a specific person catches the fungus, as it is everywhere. However, since the fungus does thrive in warm moist areas (like sweaty feet), there are certain areas one should avoid or use with caution. Shower floors, locker rooms, and swimming pools are suspected of being sources of the fungus, although there are no studies proving this fact. Nail polish and acrylic nails also make the nail less "breathable" and make the nail more susceptible to fungal infection. Fungi are everywhere -- in the air, the dust, and the soil. Hygienic measures such as spraying socks and footgear sound sensible, and perhaps these measures can even help a little bit. However, avoiding tight, nonbreathing shoes or steering clear of athletic facility floors may very well be the best prevention available. Daily washing of the feet and drying between the toes can help to prevent nail fungus. The fungi carried on the coats of pets, like cats and dogs, don't often cause nail fungus. Wearing white socks does not help.
Chronic nail trauma, such as repeatedly starting and stopping, kicking, and other athletic endeavors, can cause damage to the nails that can look a lot like fungal nails. This sort of repetitive trauma can also occur with certain types of employment or wearing tight-fitting shoes. Some traumas may cause permanent changes that may mimic the appearance of fungal nails.

Efinaconazole (Jublia) is a medication that was approved in 2014. It is a topical (applied to the skin) antifungal used for the local treatment of toenail fungus due to two most common fungal species affecting nails (Trichophyton rubrum and Trichophyton mentagrophytes). Once-daily application is required for 48 weeks. The most common side effects of Jublia are ingrown toenails and application site dermatitis and pain.
If you have diabetes or a weakened immune system, treatment is especially important. After getting a fungal nail infection, people who have diabetes have an increased risk of developing sores that do not heal. Sores that do not heal can lead to a serious health problem. It’s important to see a dermatologist (or other doctor) at the first sign of a nail problem. A dermatologist can tell you whether you have a nail infection or something else. 
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