#443 How can a runner tell athlete’s foot from contact dermatitis? - DOC

#443 How can a runner tell athlete’s foot from contact dermatitis?

How can a runner tell athlete’s foot from contact dermatitis? Well, that’s what we’re talking about today on the Doc on the Run podcast.


All right, so this question comes from Amanda, who sent this in and wanted to know how she could tell the difference between contact dermatitis and athlete’s foot.

The story goes that she basically said that it’s summertime, she’s been running, her feet sweat a lot, but she noticed a bunch of peeling skin on her feet. She didn’t think it was the skin was too dry, because her feet are always sweaty and so naturally, she assumed that it might be athlete’s foot, but one of her friends said it might be dermatitis.

So she looked up some stuff and she thought it might be contact dermatitis because she got new running socks recently. So this is a completely reasonable question and it’s a great thing to have as an episode, because this does happen.

Now, if you’re allergic to anything, whether it’s the materials in the socks, or your shoes, or the laundry detergent you use to wash the socks, you can get a thing called contact dermatitis. And it’s pretty much just what it sounds like. Dermatitis means irritation and inflammation within the skin, and it usually manifests itself as peeling, redness, itchiness, or dryness in the skin.

But a lot of times it’s just peeling skin and you can get dermatitis for lots of different reasons, but specifically, contact dermatitis is where you have basically an allergic reaction in the skin that causes peeling. If you get that, a lot of times you can tell because of the location, like if you’re wearing new leather shoes and you get irritation all over your feet, right where the shoes touch your feet, it makes it very obvious. That’s one of the most common causes of contact dermatitis, is actually things like the tannins in some leathers.

Lots of people also will get contact dermatitis from when they have a nickel allergy and certain types of jewelry, but you can get it from your socks. You can get it from laundry detergent on your socks, and there’s a variety of reasons you could get it. It doesn’t really matter that much if your skin’s dry or sweaty, you can still get it.

Now, athlete’s foot’s very common and athlete’s foot is different. Athlete’s foot, you get peeling, specifically you usually get little circular areas of peeling. Why you get that is that the fungus gets within the skin and the fungal filaments as they grow, they basically expand and separate the layers of the skin causing peeling. As it does that the fungus actually sucks the moisture out of the skin and causes what looks like a very dry blister.

But as soon as your socks or your shoes move at all against it, it just shears it off and then all you see is a little circle where you had the blister where it used to be. You just see the rim of where the blister was attached to the skin. Every time that happens, you’re shedding fungal filaments of spores in your shoes and socks though, and then it could actually turn it into a nail infection later, which is gross, and that would be a whole other topic. But anyway, back to the story here.

So how do you tell the difference? Well, it’s really simple. There’s a trick podiatrist have been using for many, many years, which we can actually tell right away which is which. We do this if we don’t really know which it is. So here’s how it goes. Basically, if you think about it, one condition is actually caused from inflammation within the skin, like an allergic reaction where your immune system goes kind of crazy and causes the skin to start exfoliate or peel. The other one is caused by a fungal infection in the skin causing the skin to peel.

What you do if you have the same kind of situation on both feet, if you really want to just test it out and see, you could maybe skip a visit to the podiatrist by doing this. You just go to the drugstore, and you get two different things. And I often tell patients, do this. I’ll tell him, okay, go get some anti-fungal spray, like Lamisil spray or Terbinafine spray.

You get that spray that you know will kill off the fungus and you start using it on your left foot. Then you go get some cream that will stop the allergic reaction, like hydrocortisone cream. So you can go and get some over the counter medications, a cream to put on your right foot that will actually treat the inflammatory reaction and it will moisturize the skin.

It does two things. On that side, if you have dermatitis because your skin is too dry, if you have dermatitis because you have contact dermatitis and its allergic reaction, it will respond to the hydrocortisone cream. You apply it according to the directions on the box, and if it goes away, then you know it was just dermatitis. Now on the other foot, if you’re doing the Lamisil spray, well, if you have a fungal infection, that side will start to improve.

Remember, if you have a fungal infection in the skin and you apply a hydrocortisone cream that actually decreases your immune system response to the fungus a little bit, and it adds more moisture to the skin that the fungus needs to thrive, well the fungus might actually get a lot worse on that side.

If you have the hydrocortisone or the steroid side on your right foot, actually gets a whole lot worse, then you know it’s not just dermatitis and it’s probably a fungal infection. And then at that point, by the time you realize that you’ll probably already see improvement on the other side, where you’ve been using the antifungal spray. So that’s really one of the simple ways to do it. It’s sort of like a simple version of patch testing that an allergist would do, or the podiatrist might do as well.

So if you think you have contact dermatitis or you think you might have a fungal infection in the skin like athlete’s foot, you could just try that approach and then you can figure it out pretty quickly all on your own.

Again, if you’re worried about that, though, if you want to get the free course on the fungal infection in the nails and the skin for runners, you can go to DocontheRun.com/fungus, and you can sign up for it free there. Thanks for listening.