In some cases of suspected nail fungus there is actually no fungal infection, but only nail deformity. A 2003 source gives a figure of 50%[17] whereas a more recent source claims that fungus is present in 65 to 95 percent of cases.[18] Avoiding use of oral antifungal therapy (e.g. terbinafine) in persons without a confirmed infection is a particular concern because of the possible side effects of that treatment.[17] However, according to a 2015 study, the cost in the United States of testing with the periodic acid–Schiff stain (PAS) was about $148. Even if the cheaper KOH test is used first and the PAS test is used only if the KOH test is negative, there is a good chance that the PAS will be done (because of either a true or a false negative with the KOH test). But the terbinafine treatment only cost $10 (plus an additional $43 for liver function tests). In conclusion the authors say that terbinafine has a relatively benign adverse effect profile, with liver damage very rare, so it makes more sense cost-wise for the dermatologist to prescribe the treatment without doing the PAS test. (Another option would be to prescribe the treatment only if the potassium hydroxide test is positive, but it gives a false negative in about 20% of cases of fungal infection.) On the other hand, as of 2015 the price of topical (non-oral) treatment with efinaconazole was $2307 per nail, so testing is recommended before prescribing it.[18]
The fungi (molds) that cause athlete's foot require warmth and moisture to survive and grow. There is an increased risk of infection with exposure to warm, moist environments (e.g., occlusive footwear—shoes or boots that enclose the feet) and in shared humid environments such as communal showers, shared pools, and treatment tubs.[17] Chlorine bleach is a disinfectant and common household cleaner that kills mold. Cleaning surfaces with a chlorine bleach solution prevents the disease from spreading from subsequent contact. Cleaning bathtubs, showers, bathroom floors, sinks, and counters with bleach helps prevent the spread of the disease, including reinfection.
Nail fungus is usually harmless. But many people find discolored or thickened nails unpleasant to look at and want to get rid of the fungus as soon as possible. Fungal nail infections can also spread, and may infect other people. Regardless of the treatment you choose, it will take a while until the nail looks normal again. It’s especially important to be patient where toenails are concerned. It can take a year for a healthy big toenail to grow back. Nail fungus can sometimes be very persistent despite treatment. It can also come back after successful treatment.

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.
Readily available over-the-counter treatments work well for most nail-bed infections, especially early cases. An advanced toenail fungus infection may require a podiatrist’s intervention. To counteract a serious infection, medical professionals may utilize prescription topical medications, oral medications, and even laser therapy.  Some cases best respond to combination therapy.

For this treatment, the affected toe or finger first has to be soaked in warm water for ten minutes and then dried. After that, the urea-based cream is applied to the nail, and the nail is covered with an adhesive bandage. After 24 hours, the bandage is removed and the toe or finger is held in warm water again. The softened layer of the nail is then scraped off using a spatula, the cream is applied again and the nail is covered with a new bandage. This treatment is carried out over 14 days. Once the infected part of the nail has been scraped away completely, the skin beneath is treated for another four weeks with a bifonazole cream.
Fungal athlete's foot may cause a rash on one or both feet and even involve the hand. A "two feet and one hand" pattern is a very common presentation of athlete's foot, especially in men. Hand fungal infections are called tinea manuum. Fungal athlete's foot may also be seen along with ringworm of the groin (especially in men) or hand(s). It is helpful to examine the feet whenever there is a fungal groin rash called tinea cruris, or jock itch. It is important to treat all areas of fungal infection at one time to avoid reinfection. Simply treating the soles and ignoring the concurrent fungal infection of toenails may result in recurrences of athlete's foot.
Athlete’s foot—the most prevalent foot fungus—thrives in warm, sweaty places like the insides of your athletic shoes, which is how it got its name. However, foot fungus can develop in multiple environments, natural and man-made, as long as there is lots of moisture where fungi can grow. These include shared areas at gyms or pools, soil and grass, or even shared items such as shoes, socks, or towels from household members who are infected.  
There are many topical antifungal drugs useful in the treatment of athlete's foot including: miconazole nitrate, clotrimazole, tolnaftate (a synthetic thiocarbamate), terbinafine hydrochloride,[17] butenafine hydrochloride and undecylenic acid. The fungal infection may be treated with topical antifungal agents, which can take the form of a spray, powder, cream, or gel. Topical application of an antifungal cream such as terbinafine once daily for one week or butenafine once daily for two weeks is effective in most cases of athlete's foot and is more effective than application of miconazole or clotrimazole.[23] Plantar-type athlete's foot is more resistant to topical treatments due to the presence of thickened hyperkeratotic skin on the sole of the foot.[13] Keratolytic and humectant medications such as urea, salicyclic acid (Whitfield's ointment), and lactic acid are useful adjunct medications and improve penetration of antifungal agents into the thickened skin.[13] Topical glucocorticoids are sometimes prescribed to alleviate inflammation and itching associated with the infection.[13]
Oral medications include terbinafine (76% effective), itraconazole (60% effective) and fluconazole (48% effective).[2] They share characteristics that enhance their effectiveness: prompt penetration of the nail and nail bed,[23] and persistence in the nail for months after discontinuation of therapy.[24] Ketoconazole by mouth is not recommended due to side effects.[25] Oral terbinafine is better tolerated than itraconazole.[26] For superficial white onychomycosis, systemic rather than topical antifungal therapy is advised.[27]
Globally, fungal infections affect about 15% of the population and affects one out of five adults.[2][21] Athlete's foot is common in individuals who wear unventilated (occlusive) footwear, such as rubber boots or vinyl shoes.[21][23] Countries and regions where going barefoot is more common experience much lower rates of athlete's foot than do populations which habitually wear shoes; as a result, the disease has been called "a penalty of civilization".[35] Studies have demonstrated that men are infected 2–4 times more often than women.[2]
Fungal athlete's foot may cause a rash on one or both feet and even involve the hand. A "two feet and one hand" pattern is a very common presentation of athlete's foot, especially in men. Hand fungal infections are called tinea manuum. Fungal athlete's foot may also be seen along with ringworm of the groin (especially in men) or hand(s). It is helpful to examine the feet whenever there is a fungal groin rash called tinea cruris, or jock itch. It is important to treat all areas of fungal infection at one time to avoid reinfection. Simply treating the soles and ignoring the concurrent fungal infection of toenails may result in recurrences of athlete's foot.
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
One of the best remedies for toenail fungus, apple cider vinegar can be used topically, internally, or both. Mix one part ACV and one part Epsom salts with six parts hot water.  Let the water cool so that it is still warm to the touch, but not so hot as to be damaging to your skin.  Soak feet up to twice daily for at least thirty minutes to kill fungus.  Mix two tablespoons of organic apple cider vinegar with eight ounces of warm water and add a teaspoon of honey to sweeten the beverage.
Wei, Y.-X., Xu, X.-Y., Xu, & Song, X. (2017). A review of antifungal natural products against the pathogenic fungi causing athletes' foot disease. Current Organic Chemistry, 21, 1–13. Retrieved from https://www.researchgate.net/profile/Xun_Song/publication/319128408_A_Review_of_Antifungal_Natural_Products_Against_the_Pathogenic_Fungi_Causing_Athletes'_Foot_Disease/links/59931c65458515c0ce61efa1/A-Review-of-Antifungal-Natural-Products-Against-the-Pathogenic-Fungi-Causing-Athletes-Foot-Disease.pdf
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