Causes of Toenail Fungus – Let’s Get Scientific

What are the actual CAUSES of thick or yellow toenails?

You know by now that you probably have AT LEAST one of the risk factors for toenail fungus AND how toenail fungus is contracted, BUT… are you still wanting to know exactly what causes this unsightly condition?

Picture of Question Marks

FOREWARNING… In order for me to discuss the exact cause of toenail fungus it doesCauses of Toenail Fungus require me to get a little scientific on you!

Bear with me and just think of how smart that you can sound at your next family gathering!

Let’s get to it…

 What Causes Toenail Fungus?

“Why are my toenails thickening?” and “Why are my toenails yellow?” are common questions that I hear in-office on a day-to-day basis.

If you will remember from What is Toenail Fungus?, I briefly touched on the fact that one of the most common causes of thick and yellow toenails is a prevalent condition called toenail fungus.

There, I stated that most of the time fungi and sometimes candida, or yeast, were the culprits of this condition among other conditions such as Athlete’s Foot.

Causes of Toenail Fungus - Mold

I do not want you to come to the conclusion that all fungus is harmful.

In fact, some fungi actually DO have beneficial uses. But… that is not the case for the fungi that we will discuss here.

The little microscopic organisms that we will be talking about ARE harmful, AND they have the potential to cause the dreaded toenail fungus with symptoms such as thick, yellow and crumbly toenails as well as other conditions like foot fungus.

The Science Behind Toenail Fungus

So… let’s delve deep into the question, “What causes toenail fungus?”.

Buckle up… here we go!

Causes of Toenail Fungus - Fungus

We have already eluded to the fact that toenail fungus, as well as Athlete’s Foot, is caused by fungal organisms.

More specifically though, these fungal organisms can be broken down into three main categories:

  • Dermatophytes,
  • Candida and
  • Nondermatophytic Molds.

You knew this would get more complicated, right?

Remember… these are ALL tiny, microscopic organisms!

Each of these three categories can be further divided.

The most Picture of Trichophyton rubrum - Common Cause of Toenail Funguscommon toenail fungus-causing dermatophyte is Trichophyton rubrum, but other dermatophytic causes of this infection include, but are not limited to, Trichophyton interdigitale, Epidermophyton floccosum, Trichophyton violaceum, Microsporum gypseum, Trichophyton tonsurans and Trichopyton soudanense.

As stated above, though, Candida (yeast) as well as Nondermatophytic molds can also be culprits.  Neoscytalidium, Scopulariopsis, and Aspergillus are common molds that may cause the unsightly presence of toenail fungus.

This is all not really importance, but I wanted to include for completeness sake!!!

More on the Causes of Toenail Fungus

Remember, fungi naturally live in warm, moist environments such as shower areas and swimming pools; so, it is difficult to completely avoid contact with these tiny organisms.

What do we typically do in these damp areas?

You guessed it… we walk barefoot! Fungi loves this!!!

Barefoot at the pool

If you will also remember from What is Toenail Fungus?, these organisms, or pathogens, usually enter the area of infection through tiny cracks, cuts, or small skin separations (usually between the nail plate and nail bed).

In addition, remember from Risk Factors for Toenail Fungus that a prior injury to the nail bed may make this area more susceptible for the fungus to enter the area.

They make contact with you, hold on and then multiply!Picture of a Locker Room for post What Causes Toenail Fungus

Because the toenails and feet are more prone to direct contact with these fungi via walking barefoot in swimming pool areas, shower areas, and locker rooms, this makes them more likely to develop an infection as compared to other parts of the body .

Fungi are able to multiply extremely rapidly within the toenail. This is due to the fact that the nail covers the area and provides the fungi with a warm and moist environment… a perfect environment for the fungi to thrive.

The special thing about these organisms is that they do not require sunlight to survive.


Be Proactive – Prevent Toenail Fungus

Causes of Toenail Fungus - Be ProactiveWhen you have one or more risk factors with no preventative measures in place AND are regularly exposed to these little critters, toenail fungus is SURE to be knocking at your door!

The best thing you can do is prevent, prevent and prevent nail fungus from EVER taking up shop in the first place!


If you already have toenail fungus, you must treat this condition first and THEN put preventative measures in place to prevent contracting this unsightly condition again!


Go to next section: Symptoms of Toenail Fungus

Skip the educational information and go straight to MY PERSONAL TREATMENT RECOMMENDATIONS FOR TOENAIL FUNGUS!!!

12 thoughts on “Causes of Toenail Fungus – Let’s Get Scientific

  1. Amazing article on toenail fungus, you have done a great job researching toenail fungus and shared every aspect anyone could possibly be curious about. Very good photographs as well showing toenail fungus, I am sure many people have this problem and never knew it was actually a fungus until reading your article today.

    Very good treatment plan as well you suggest in this article, I will be sure to save this article and pass it along to my family and friends.

    1. Thank you so much for taking the time to read the article! Hopefully you will never have to face this issue! Should you have any questions or concerns in the future, please feel free to comment! ((:

  2. Dr. Misty — Great article!

    You are soooo right. When it is a damp area, we typically walk barefoot. Heck, I just did it today after I cleaned the mudroom out from our pets mess. I used a spray with tea tree oil to help as an antifungal; however, since I have three pets that frequent that area I always feel like it is never clean enough.

    Very insightful article and I learned a lot about toenail fungus. Gotta pass this one on to my Aunt in Georgia. She has battled severe toenail fungus for over a decade to no avail!

    Thanks again,

    Nerissa S.

    1. Nerissa S.,

      I totally understand how easy it is to venture into some areas where the contraction of toenail fungus is most common! I do also on a weekly basis!

      I do want to commend you on your use of a tea tree oil spray as a preventative way to avoid contraction of a toenail fungus! Great job!

      Please do forward to your aunt in Georgia! I have seen some of my patients spend so much money on both treatments that just do not work as well as treatments that could have long-term effects on their bodies!

      There are currently THREE treatments that I consistently recommend to my patients for the treatment of toenail fungus! You can review them by clicking HERE! They are currently the most effective treatments on the market and I have witnessed the ability of each of these to combat this unsightly condition on thousands of my patients. Also… none of them will put you at risk for all those nasty side effects that you see in so many of the others!!!

  3. Yeah, I have one discolored nail. Tried everything and nothing works. Tea tree oil, anitbiotics…etc. I was going to ask what would you recommend for toe nail fungus. But I looked around your site and found your recommendations. I am definitely going to order one of the three that you suggest and try it.

    1. Hey Dave! Yes!!! I get a lot of that! People that have tried numerous things and nothing works… including plain tea tree oil!

      Out of the three products that I recommend, two include a topical solution. With both of these two, Purely Northwest Foot and Toenail System and Zeta Clear Nail Solution, tea tree oil is one of the main ingredients. Where most products fail and how these two are so effective is the therapeutic dosage of tea tree oil along with the other natural ingredients included within these products. That is what makes these two topical options that I recommend work so efficiently!

      I hope that you will come back to my site and report your progress as I know that you will be ecstatic with your results on any of my recommended treatment options!

  4. I used to have yellow fungus on my toenails. I think they liked the sweaty atmosphere of inside my socks, there’s a first.

    Due to working long hours for years without time off, my feet were constantly covered with socks and athlete’s foot was a common problem too.

    Thanks for educating me on the various feet fungi,

    1. Hello Simon!

      Fungus absolutely does love sweat! It can thrive when exposed to this environment! Feel free to click HERE to learn how sweat is a risk factor for fungus!

      Also… it is best to treat your conditions as quickly as possible… the fungus will ONLY worsen! I have also included a link to the products that are most successful in treating toenail fungus. Click HERE to read a review of these products!

      Just let me know should you have any additional concerns or questions! I am here to help!

  5. Thanks for this valuable information on the causes of toenail fungus. My aunt actually has thick, yellow toenails and I was wondering what caused this. Now I know!

    I had a question about sharing shoes with someone that has toenail fungus… is there a way to ensure that I will not contract this from the shoes of somebody that has it? I do like to share shoes with my aunt. Now I am nervous to do so. Is there something that I should be doing? How can I clean this fungi out of shoes?

    1. Hello Nicole and thank you for visiting my post on causes of toenail fungus.

      On to your question… there definitely IS a way to share shoes with someone that has toenail fungus without the worry of contracting this unsightly disease! You MUST use a shoe sanitizer! I discuss shoe sanitizers in my post titled, “The Best Shoe Sanitizer – Does It Exist?“. Also… I have a review on MY ABSOLUTE FAVORITE shoe sanitizer. You can read all about it by clicking HERE!

      I hope that helps! Should you have any further questions or concerns please feel free to leave a comment and I will definitely get back with you! ((:

  6. I am embarrassed to say that my some of my toe nails are a bit thick. I went to a doctor and they cut off a sample. The result was that it wasn’t fungi, but I don’t think that that is correct. I think that it is fungi.

    I’ve seen so many products on the market that I do not know which one to go for. Which one would you recommend? Is there a natural remedy? And how long can you expect for the toenail to get better?


    1. Hello Owain and thank you for visiting my article on the causes of toenail fungus.

      I have to admit that nail biopsies are performed much too frequently AND all too often we see false negative results. This means that fungi is really present, but you get a negative biopsy result. So… these nail biopsies are not 100% accurate.

      I am sorry that you have been fighting with thick, yellow toenails. I do have a post on natural home remedies to cure toenail fungus. You can reach that post by clicking HERE.

      There ARE cures for this condition. I actually can recommend three different products that work amazingly to combat toenail fungus. You can read about all three of these products HERE. Two of these three products are made of 100% natural ingredients. The Purely Northwest Foot and Toenail System is purely topical while the Zeta Clear Nail Solution includes both a topical solution and oral homeopathic spray.

      The third product that I recommend, Cure Ex Laser, is an at-home laser treatment to fight toenail fungus.

      The take-home on this is that you have to pick a treatment (you won’t find any that work more efficiently than those three listed above) and stick with it. There is currently NO way to cure toenail fungus over night! While you will see benefits within a few weeks of treatment with any of the products listed above, it does take about 4-6 months and sometimes even longer to fully heal toenail fungus.

      I hope this helps! Should you have any additional questions or concerns, please feel free to comment any time and I will get back with you. I truly am here to help! ((:

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