Toenail fungus is a common fungal condition that often starts after a rash on the foot spreads to the nails. When mild, it looks like white and yellow spots growing under the nail beds.

Toenail fungus, also known as onychomycosis is a condition where your nails are infected by fungi that make your toenail look yellow, brittle, and ragged. Toenail fungus is a common condition that people often experience but although the condition doesn't cause any pain in most cases, it can be quite irritating to see that your nail isn't clean and has thickened fungi and yellow stains on it. Toenail fungus is one such thing that makes a person insecure about how their toenail looks and always finds it as something unhygienic.

 

People often treat toenail fungus by using antifungal and antibacterial medication including both oral and topical medication. In most cases, these medications do provide relief from toenail fungus for a short time. But the problem with these medications is that they don't provide permanent relief and the toenail fungus happens to recur. So it is apparent that the common medication used to treat toenail fungus isn't as effective as we believed it to be. Have you ever given thought to why it is impossible for antifungal medication to remove fungus from your body once and for all? It is because these medications don't treat the root cause of toenail fungus and also fail to kill off the spores of the fungi. Also when your body is supplied with a lot of antifungal medications, the fungi tend to grow an antifungal resistance which makes these medications futile. In addition to these, since antifungal medications aren't completely natural ones, there are many safety concerns surrounding them.

 

So as antifungal medications are an ineffective way to get rid of toenail fungus, the next option that we have are supplements. In the past few months, we have seen a rise in the number of over-the-counter toenail fungus treatments which largely include natural supplements that are claimed to be aiding in eradicating toenail fungus permanently and are more effective than other medications. People have been choosing these supplements to treat toenail fungus. As more and more people are opting for natural supplements over antifungal medications, the demand for supplements is increasing as the number of them available is also increasing. Although natural supplements are considered an effective way to treat toenail fungus, it doesn't mean that everyone is effective. Some might and some might not be. But identifying which one is effective and which one isn't from the clutter of them can be quite a task. This is why we have curated a list of the best toenail fungus treatments that is an effective and safe ways to eliminate toenail fungus permanently.

 

In this article, we will be taking an in-depth look at some of the best toenail fungus treatments and will discuss their various aspects. We will also be talking a little bit about a few things you should look at in a toenail fungus treatment before buying it so that you will be able to make an informed decision.

 

Our Rankings of the Best Fungus Treatments

 

If you are looking for the best treatment for toenail fungus, consider these top picks:

• Kerassentials (4.8/5) - This nail fungus treatment oil is highly recommended for its effectiveness in treating nail fungus.
• Clavusin (4.7/5) - This over-the-counter treatment is a popular choice for those who want a convenient and effective solution for their toenail fungus.
• Metanail Serum Pro (4.5/5) - Metanail Serum Pro is a 20-in-1 nail health support formula that is popular for its effectiveness in treating toenail fungus.
• Keravita Pro (4.3/5) - This supplement is known to be the best for treating fungal infections from the inside out.
• Mycosyn Pro (4.1/5) - These natural capsules are a great choice for those who prefer a more natural approach to treating toenail fungus.

 

#1. Kerassentials - Best Overall

 

 

The first one in our top picks of the best toenail fungus treatment is the doctor-formulated formula, Kerassentials. Kerassentials is an entirely natural formula that is created by using scientifically backed ingredients that has the capability to eliminate fungus from toenail permanently. As per the creator of Kerassentials, the formula is capable of removing fungus from your toenail and cuticle and also restricts the mutation of it, ensuring that they aren't even a spore of fungus present in your toenail. The formula is a proprietary blend of natural oils and minerals and it is said that every ingredient of Kerassentials is of premium quality.

 

One main reason why Kerassentials has a position in the list of best toenail fungus treatments is that the formula provides you with every benefit without causing any side effects on your skin such as any irritation or itching. The formula is also completely odorless and colorless. Kerassentials is presently available on the official website of the supplement at an affordable cost in three packages.

 

Pros

• A completely natural formula that has high-quality ingredients in it.
• Targets the root cause of toenail fungus and restricts its mutation.
• Kerassentials is manufactured in a GMP-certified and FDA-registered facility.
• The formula is free of artificial stimulants and genetically modified contents.
• Supported by a risk-free refund policy.

 

Cons

• Available only on the official website of Kerassentials.
• Children are restricted from using the formula.

 

Ingredients of Kerassentials

 

As aforementioned, Kerassentials is an entirely natural formula that has only natural ingredients in it. Let's take a quick glance what these natural ingredients and what the health properties they possess:

• Lavender oil: Lavender oil is one of the primary ingredients of Kerassentials and the oil is popular for its ability to support nail and skin health. Lavender oil fights against toenail fungus and protects nail keratin ensuring that your nail is immune to further fungus attacks.
• Organic flaxseed oil: Organic flaxseed oil plays a huge role in boosting your nail and skin immunity. This ingredient also supports the healthy regrowth of nails and removes yellow stains from your nails.
• Almond oil: Almond oil prevents the mutation of fungus and also kills off its spores. The oil also protects your nail from infection and boosts the overall health of your toenail.
• Tea tree oil: Tea tree oil is an ingredient that has numerous antifungal properties which help in treating toenail fungus. Tea tree oil also curbs the growth of fungus and also assists in the growth of healthy nails.
• Lemongrass oil: Lemongrass oil is an efficient antifungal that prevents infection and also helps with inflammation.
• Aloe vera: Aloe vera is also an antifungal and is greatly used by many because of its ability to smoothen your skin
• DL-alpha-Tocopherol: DL-alpha-tocopherol is the stable form of vitamin E that protects your skin and also moisturizes your cuticle
• Isopropyl palmitate: Isopropyl eradicates fungus spores from your toenail, clears your skin, and supports healthy nails.
• Undecylenic Acid: Undecylenic acid is a beneficial fatty acid that prevents fungal infection and also protects your nails.

 

Manufacturing Standards

 

Now let's talk about the manufacturing standards and quality of Kerassentials. The natural formula is crafted in an FDA-approved and GMP-certified facility in the United States of America. As per Kerassentials' official website, the formula does not have any kind of chemicals or artificial stimulants in it and is also non-GMO.

 

Side effects

 

Since Kerassentials is a natural formula, the possibility of experiencing any side effects from the formula is minimal. The manufacturer assures that you will not feel any itching or irritation when you apply Kerassentials to your nail.

 

How to use Kerassentials

 

Apply the formula to your nails four times a day (twice at noon and twice in the morning ) using the enclosed brush. You can also apply it on your cuticle and skin near your toenail using a cotton swab.

 

Customer reviews

 

Kerassentials has been and is still one of the most popular toenail fungus treatments and hundreds of customers have already used the formula. The majority of the customers of Kerassentials are positive ones and there aren't any reviews that report a side effect.

 

Kerassentials is protected by a hassle-free refund policy. The manufacturer of Kerassentials offers a 60-day money-back guarantee offer on every order of Kerassentials.

 

Visit The Official Website Of Kerassentials Oil

 

#2. Clavusin

 

Clavusin is a nutritional supplement featuring a blend of classic detoxification agents – like bentonite clay and fiber. By taking the oral supplement daily, you can support your body's natural cleansing processes, helping to remove toxins and other harmful ingredients from your body.

 

Clavusin uses bentonite clay, Lactobacillus acidophilus, glucomannan root, and other natural ingredients to push waste out of your body. If you have fungal overgrowth in your gut, then Clavusin could help support your body's natural defenses, which could help eliminate the root cause of nail fungus.

 

According to the official website, Clavusin can also lighten toenails, make odor disappear, fix the color and texture of your nails, and even eliminate varicose veins, among other benefits. Just take two capsules daily to support your body's natural cleansing processes.

 

Pros

• It eliminates toxic substances and free radicals from the body.
• Clavusin addresses inflammatory processes.It decreases oxidative damage.
• The supplement promotes cell regeneration.
• It lowers the risk of bacterial build-up and infection spread.
• Clavusin supports immunity.
• The product eases pain, itching, skin flaking, irritation, etc. caused by nail fungus.
• It supports metabolic performance.
• It restores energy.
• Clavusin may improve mood and boost self-confidence.
• It comes with a 2-month full refund guarantee.

 

Cons

• The results aren't immediate.
• Clavusin is available through the original manufacturer only. You won't find it online.

 

Ingredients

So, Clavusin is a fully organic product. Only natural components are used in the potent mix. All the ingredients have been selected based on their antioxidative and anti-inflammatory properties. Let's take a closer look at the formula, shall we?

• Plantain: This plant soothes the nerves and eases pain, itching, burning sensations caused by nail fungus. Also, it eliminates toxins and free radicals from the organism.
• Glukomannan: It supports immunity and takes part in the body's detoxification. By purifying blood, it reduces the risk of infection spread.
• Bentonitic clay: This component alleviates inflammatory states, reduces pain caused by fungi, and improves the condition of the skin surrounding infected nails.
• Juglans nigra: Also known as black walnut, it treats nail fungus, stops the build-up of bacteria, reduces oxidative stress, and promotes the healing process.
• Lactobacillus acidophilus: This probiotic strain improves metabolic performance and the gut microflora. Thus, it reduces the risk of intoxication and mycoses of the alimentary tract.

 

Manufacturing Standards

The manufacturing of the Clavusin product takes place in GMP-certified and FDA-approved facilities that meet the strictest hygiene standards. It contains the only pure ingredients which are 100% legal and safe for use.

 

Side effects

Clavusin is a fungus supplement that has been developed for any age and for all medical conditions. It tackles the root of itching, skin rashes, and discomfort.

Clavusin contains only natural ingredients. So Clavusin is completely natural and 100% non-invasive, and absolutely risk-free!

 

Hot to use Clavusin

Clavusin is meant for oral administration: consumers should take the supplement in 2 capsules on a regular basis. The manufacturer recommends using the product in the second half of the day after lunch or dinner. Thus, the formula will be absorbed better. Take the capsules with a glass of water or any other beverage to your liking, except alcohol.

 

Customer reviews

Customer testimonials let you know everything about a product, and you should always choose supplements with good customer reviews. Fortunately, all the Clavusin reviews seem to be positive. The supplement is not only safe but also worth your investment.

 

Visit The Official Website Of Clavusin

 

#3. Metanail Serum Pro

 

Metanail Serum Pro is an advanced formula that is created by using scientifically backed natural ingredients that promotes all aspects of your nail health. The research team behind the formula says that Metanail Serum Pro can help in eliminating toenail fungus, restores healthy nails, keep your nail and feet moisturized, and so on. The formula has only natural ingredients in it and all of them are of high quality.

 

Metanail Serum Pro is manufactured in an FDA-registered and GMP-certified facility in the United States and each container has been tested for its safety and purity before it was sent out to the market. The formula helps in restoring your nail health and eliminating toenail fungus without causing any adverse side effects which makes it a good choice for improving your nail health.

 

Pros

• Metanail Serum Pro is an entirely natural formula that aids in eliminating toenail fungus without causing any negative side effects.
• Metanail Serum Pro supports every aspect of nail and foot well-being.
• The natural formula promotes healthy regrowth of nails.
• Metanail Serum Pro is manufactured in an FDA-registered and GMP-certified facility in the United States.
• The formula is backed by a money-back guarantee.

 

Cons

• Metanail Serum Pro is available only on its official website.

 

Ingredients

 

• Witch Hazel: Witch hazel is a shrub that is native to North America and is a common ingredient used in American folk medicine. The ingredient can help in treating toenail fungus and also reduces skin irritation.
• Gotu Kola: Gotu Kola is an ingredient that is used in Chinese, Indonesian, and Indian traditional medicine to treat various health conditions. The ingredient improves your toenail immunity and protects them from infections.
• Rosemary: Rosemary is an ingredient rich in antioxidants and anti-inflammatory properties. The ingredient promotes nail health by keeping your nails and cuticles moisturized.
• Glycerin: Glycerin is an ingredient that is popular for its ability to keep your skin and nail moisturized. The ingredient also hydrates the outer layer of your skin and nail.
• Lemon Peel Extract: Lemon peel extract is a great source of calcium and vitamin C and helps with nail fragility and breaking. The ingredient also has properties that rejuvenate your nail.
• Vitamin C: Vitamin C is an ingredient that is filled with antioxidants that improve nail health. The ingredient also removes yellow stains from your nails and keeps them white and clear.
• Vitamin E: Vitamin E is known for its ability to treat yellow nail syndrome and helps in removing stains from your nails. The ingredient also keeps your nail and feet moisturized and hydrated.
• Hyaluronic Acid: Hyaluronic acid is an ingredient that is well known for its moisturizing properties. The ingredient also aids in maintaining nail health integrity and boosts its immunity.
• Sage Leaf Extract: Sage leaf extract helps in improving your nail health by keeping them moisturized and provides nail and feet comfort.

 

Manufacturing Standards

 

As already mentioned, Metanail Serum Pro is manufactured in an FDA-registered and GMP-certified facility in the United States. The official website of the formula says that it is non-GMO and does not have any kind of artificial stimulants or synthetic filler in it.

 

Side effects

 

As Metanail Serum Pro has only natural ingredients and all of them are of high quality, the chances of the supplement giving rise to any adverse side effects in your body are minimal to nil. The manufacturer assures that the supplement will not cause any irritation on your skin or nails once you apply it.

 

How to use Metanail Serum Pro

 

Metanail Serum Pro comes in the form of a liquid that you need to apply to your nail. The manufacturer of the formula provides usage instructions on every bottle of Metanail Serum Pro onto smooth skin or nails without fail in the morning and evening to achieve maximum benefits.

 

Customer reviews

 

Metanail Serum Pro has received majorly positive reviews from its customers. Many of the customers of the formula have shared their experience with it on different online platforms, and most of them have said that the Metanail Serum Pro worked effectively for them.

 

Visit The Official Website Of Metanail Serum Pro

 

#4. Keravita Pro

 

Keravita Pro, similar to Kerassentials, is a popular toenail fungus formula that assists in getting rid of toenail fungus. Keravita Pro is an all-natural toenail health support formula that works on removing toenail fungus internally. Keravita Pro is an oral toenail fungus treatment that primarily focuses on the root cause of toenail fungus and removes them completely from your nail once and for all. The creator of Keravita Pro says that the supplement is an effective one that assists in removing nail fungus, keeps your feet clean and dry, and enhances your overall toenail health.

 

Keravita Pro is a blend of natural ingredients that have been scientifically proven to be effective in enhancing toenail and foot health. When you consume the blend of these ingredients as tablets, your feet and nail health will enhance. Keravita Pro does not have any adverse side effects associated with it and is completely safe to consume.

 

Pros

• Keravita Pro is an entirely natural supplement that has scientifically supported ingredients in it.
• It removes fungus from your toenail without causing any side effects.
• Keravita Pro enhances nail, feet, and skin health.
• The supplement is created in the USA in an FDA-approved and GMP- certified facility under strict and sterile conditions.
• The supplement is protected by a money-back guarantee.

 

Cons

• People below the age of 18, pregnant women, and breastfeeding women are restricted from taking the supplement.
• If you are taking any medication, it is wise to consult a doctor before using Keravita Pro to ensure that it won't interact with your medicines.

 

Ingredients of Keravita Pro

 

Let's take a quick glance at the ingredients of Keravita Pro and its health properties:

• Vitamin C: A primary ingredient of Keravita Pro is vitamin C and it is filled with antioxidants that can enhance your skin health. Vitamin C also has antifungal properties which help in fighting off toenail fungus.
• Vitamin E: Vitamin E is considered a topical therapy that can help in the treatment of toenail fungus. It also supports nail and foot health by preventing cracked cuticles and keeping the nail around your nails moisturized.
• Selenium: Selenium is a powerful antifungal agent that can assist in removing fungus from your toenail. Selenium also helps in brittle nails and also removes yellow stains from your nails.
• Burdock: Burdock is a plant endemic to Japan and has many health properties. Burdock can enhance your nail health by ensuring that the fungus doesn't mutate and moisturizes your cuticle.
• Graviola leaf: Graviola leaf has many anti-infectious properties which ensure that your toenail is protected from any fungal infections. Graviola leaf also boosts the immunity of your skin and nails.
• Panax Ginseng: Panax ginseng is an ingredient that is enriched with antioxidants, vitamins, and minerals. The ingredients have the ability to enhance your toenail health and also make your skin more smooth.
• Lycopene: Lycopene is a powerful antioxidant that removes free radicals from your toenail and feet. This ingredient detoxifies your feet including your toenails and removes fungus and its pores.
• Olive leaf: Olive leaf is a clinically proven ingredient that is effective in removing toenail fungus. The ingredient has antiviral and antibacterial properties that assist in eradicating toenail fungus.
• Turmeric: It is a well-known fact that turmeric is an ingredient that possesses numerous skin health properties. One such is the antiseptic properties, which help in treating toenail fungus and the ingredients also enhance nail health.  

 

Manufacturing Standards

 

Keravita Pro is a premium quality supplement that is manufactured in an FDA-approved and GMP-certified facility. As per the official website, every ingredient of the supplement is sourced from trusted farmers that don't use any pesticides or chemicals in it. The formula is also non-GMO and does not contain any toxins.

 

Side effects

 

Keravita Pro is a blend of plant-based ingredients, minerals, and vitamins. As mentioned above, the supplement does not contain any dangerous toxins or stimulants in it which ensures that it is safe to use and free of any adverse side effects.

 

How to use Keravita Pro

 

As per the official website, the right dosage of Keravita Pro is two capsules per day. You will have to take the capsules with a glass of water at any time that you prefer.

 

Customer reviews

 

Keravita Pro has numerous satisfied customers who have said that the supplement has aided in treating their toenail fungus and is an effective one. The customers of Keravita Pro have said that the supplement also supports nail and skin health and improves them. They said that they didn't experience any side effects while using Keravita Pro.

 

Keravita Pro is protected by a 60-day money-back guarantee. This means that you have the option to gain a refund from the manufacturer if you are not with the result that Keravita Pro has given you.

 

Visit The Official Website Of Keravita Pro

 

#5. Mycosyn Pro

 

Mycosyn Pro is one of the supplements containing all-natural ingredients that can easily help you get rid of fungal infections. This article is for you if you need a good fungal infection supplement to help you get rid of subcutaneous or superficial fungal infections.

 

To do that, Mycosyn Pro contains a blend of plant-based nutrients, vitamins, and minerals. Many of the ingredients have their roots in traditional medicine. There's horsetail, fo-ti, and spirulina, for example, all of which have a long history of use in traditional medicines around the world.

 

Mycosyn Pro is a dietary supplement with anti-fungal properties. The supplement features natural ingredients and helps get rid of fungal infections. The supplement is a product of two experts in the healthcare industry: Ayush Mahanti and Michael Davis. According to the duo, this anti-fungal supplement works well because it has natural ingredients backed by scientific studies. Hence, the Mycosyn supplement fights the underlying causes of fungal infections and can prevent future fungal infections. 

 

Pros

• No subscription.
• No extra or hidden charges.
• 60-day refund.
• Natural ingredients.
• Enjoy great-looking nails.

 

Cons

• No trial package is available.

 

Ingredients of Mycosyn Pro

 

Mycosyn Pro is highly efficient due to the ingredients used in the product. Each tablet of this product contains herbs, natural vitamins, and plant extracts.

 

Mycosyn tablet has natural vitamins, herbs, and plant extracts. All these ingredients are active and responsible for Mycosyn's excellent performance. Like any other high-performance supplement, the ingredients determine if the effects will be top-tier. Hence, without further ado, here are the ingredients:

• Horsetail: Is a perennial herb used by the Greeks and Romans as a traditional medicine. Horsetail, also known as Equisetum, improves the user's skin, hair, and bone health. The silicon content in the herb is the reason for the listed benefits.
• Saw Palmetto: Has been used to create a variety of ailments over the years. Users use a species of palm to treat urinary tract infections. Furthermore, the palm is nutritious and improves enzyme processes in the body.
• Fo-Ti: Is an Asian plant used by locals as an anti-aging remedy. Fo-Ti, also called Reynoutria Multiflora, is administered directly to the skin to cure sores and itching caused by fungi.
• Spirulina: Alga is a superfood that includes phenolic extracts that have high anti-fungal effects. It blocks out fungi by stopping glucosamine from forming in the body. Spirulina is a blue-green marine alga stacked full of protein and vitamin B. Spirulina is an endurance enhancer that the Aztecs first used.
• Vitamin C: Is also known to scientists as L-ascorbic acid. Additionally, Mycosyn Pro vitamins are one of the planet's safest and most efficient supplements. It has some positive effects on the skin's health. 
• Folate: Is a form of vitamin B commonly found in different foods. People know Folate as Vitamin B9, found in foods like green leafy vegetables, beans, and citrus fruits. Vitamin is key in the development of cells and their functions. It also helps in the fight against fungal diseases. 
• Biotin: Like Folate, Biotin is also a form of vitamin B. It is known better as Vitamin B7, found in foods like eggs, bananas, and milk. Biotin or Vitamin B7 deficiency is a common cause of hair loss and facial rashes. Hence, Biotin is a common solution for the poor health of hair, nails, and skin. 
• Alfalfa: Is a grass commonly known as Medicago Sativa. Users highly value its rich vitamins, minerals, and protein content. Alfalfa has a high concentration of Vitamin C, K, folate, and manganese. Users of this grace often use it to promote healthy blood sugar and improve cholesterol levels. 
• Barley Grass: Is the leaf of immature barley plants yet to develop seeds. Barley grass is a good booster of intestinal health. Additionally, Barley Grass provides good antioxidants, vitamins C and A. Interestingly, the ingredient has a high nutritional value. 

 

Manufacturing Standards

 

The brand also claims to manufacture its Mycosyn Pro supplement in a GMP-certified and FDA-approved facility within the United States under hygienic and sterile conditions. This Mycosyn Pro supplement comes in a 30-capsule container. Mycosyn Pro capsules do not contain stimulants and are GMO-free, non-habit-forming, and toxin-free. Furthermore, the product is meant to work for people of all genders, ages, or body types.

 

Side effects

 

Since Mycosyn Pro has all-natural ingredients, the side effects are to the barest minimum. All the ingredients in this product went through rigrous clinical testing to ensure their safety. However, these ingredients are safe only within specified amounts. Furthermore, the brand is approved by the FDA and GMP. Hence, they use the right facilities and produce their products in the best environment.

 

You can bet that each batch leaving the manufacturer is in the best shape and of the greatest quality. However, Mycosyn Pro isn't suitable for persons under 18. It is also not ideal for pregnant or nursing mothers. Furthermore, if you have any significant medical conditions or are already on prescribed pills, don't take this supplement on your own. In addition, if you have allergies, make a clean sweep of all the ingredients in the product.

 

How to use Mycosyn Pro

 

By taking two capsules of Mycosyn Pro daily, you can purportedly cleanse your system while also promoting unique benefits. The supplement claims to boost fluid retention to keep your skin hydrated, for example. It even claims to affect melanin in your skin to boost the appearance of your toenails and surrounding skin.

 

Customer reviews

 

A vast majority of Mycosyn Pro has positive reviews from customers. Many customers testify to their body's complete change after using this supplement daily. Many of these testimonials are accessible on the brand's official website.

The product has a few rare negative reviews as well. However, these reviews are from users who expected rapid changes and wanted more since the product took a while to manifest. Hence, note that you should expect the effects of this supplement after a month of constant usage.

 

On a general note, users of this product were ecstatic with the results they got from using it. Furthermore, the customer service is satisfactory and the perfect icing on the cake.

 

Visit The Official Website Of Mycosyn Pro

 

Bonus: Top Toenail Fungus Guide & Alternative Remedies of 2023

 

Eliminating toenail fungus may require more than just a supplement. You may need a step-by-step guide.

 

Fortunately, you can find toenail fungus guides explaining simple changes you can make to eliminate toenail fungus and prevent it from returning.

 

You can also find at-home therapy devices designed to cleanse nail fungus at home without the cost or embarrassment of a medical clinic.

 

We read dozens of top toenail fungus guides and tested today's top home nail fungus therapy products. Here are the ones that consistently worked:

 

Blue Heron Health News: Overcoming Onychomycosis

 

Blue Heron Health News has a long history of publishing alternative treatment guides for illnesses and diseases. In Overcoming Onychomycosis, author Scott Davis explains some of the best natural remedies for toenail fungus infections – including strategies you can implement today.

 

Onychomycosis is the scientific term for nail fungus infections. It affects approximately 1 in 10 people worldwide. It's under-discussed because it's an embarrassing and visible problem.

Scott Davis wrote Overcoming Onychomycosis on the assumption many nail fungus treatments fail. Some drugs kill 99% of fungus, for example, and leave behind 1% of superpowered fungus strains, making it increasingly difficult for your body to fight infections.

 

Instead of following conventional medical treatment for your nail fungus problem, Scott Davis recommends promoting blood flow, boosting antioxidant levels, and eating specific types of foods. You get lifetime access to the eBook for a one-time fee.

 

Visit The Official Website Of Overcoming Onychomycosis