Jun 09 2008
What’s On My Legs?
OK… It’s not the Bird Flu… and I’ve ruled out Dengue Fever. So why have I gotten this rash on the top of my legs the last two times I’ve been on the bike. I was in the heat/sun for a while on both rides. Last Thursday’s ride was 60 miles and then yesterday’s ride was 70 miles. As you can see by the pics, they’re reddish bumpy splotches on each of my quads. It doesn’t hurt… no itch… no pain… maybe a slight burn feeling… very slight. 
I say heat rash because the two times it has happened the temperature was in the upper 90’s and it felt even hotter. I was also in direct sun most of the time. Now, I do use Coppertone Sport, a waterproof sunscreen. It’s one I have always used and never had a problem. But could it be a combination of that… the heat and all the salt on my body 
from sweat? I just don’t know. I’ve ridden in hot conditions in the past and never experienced anything like this.
STOP THE PRESS! How funny… as I wrote the paragraph above… I remembered a random comment from Ron (Cozy Beehive) talking about how some waterproof sunscreens might make you overheat by blocking the sweat from escaping your body. We were talking about getting too hot and needing more fluids than normal. Well check this out. I just went back and found this under a heat rash description:
“If sweat cannot reach the skin’s surface, it may break through the duct wall and remain trapped in an inner layer of the skin, where it can cause inflammation and a rash.”
So, maybe Ron solved this before it even happened. Has anyone else experienced the same? Let me know because a second opinion never hurts (no offense Dr. Ron).
Dear David Millar, I mean Donald.
I think Ron is right. Those films don’t work preferentially in either direction. Try some cheap regular sun screen and see how it goes.
Chris– Hilarious… I knew that was coming. I’m going to have to start wearing some long white leg covers so I don’t turn into a gargantuan sized strawberry. And yes- the experiment begins with other kinds of sunscreen.
My riding buddy yesterday at the 100 miler had the same problems, he said his legs were burning up. He did mention he had sunscreen on…Another anecdotal evidence ?
Ron– Good case work! You must watch a lot of ER or Grey’s Anatomy…
Thanks for the input. I’m definitely switching up on the sunscreen before, as Chris says, I turn into David Millar.
Looks like a sunburn!
Hi Judi– I wish it was. It’s weird… my arms are fine… the rest of my legs are fine. Just freaky.
I wear a short that has a rubber band at the leg (Craft). It seems I get heat rash at that very spot just past the shorts. Has this happened to anyone…could it be the shorts?
RENEE– Actually, the heat rash I had seemed to be a little more concentrated at the leg ban as well. Maybe that was also due to the skin not be able to breath as much or release sweat because of the tight band…?
So I’m not the only one!! I’m sitting here tonight with the exact same rash on the tops of my thighs, Googling about to see what’s the cause. I’ve gotten the rash several times the past month while riding in hot/sunny areas. As chance would have it, I also use the same Coppertone Sport sunblock you do… but I already did the test of not putting any on (at least on my legs) and I still got the rash after a ride. Just like your rash in the pictures, mine has a clear line where it starts just beyond the gripper of the shorts - which A) lets me rule out any sort of allergy to the elastic, and B) makes me think it is directly related to sun exposure. Look up sun poisoning, or more specifically “Polymorphous light eruptions”, it sounds and looks spot-on to what we’re currently experiencing. They say a good way to prevent it is to slowly start exposing your skin to the sun in the early parts of the year so that when the sun is at its most intense (now) your skin will be conditioned. I know for me that this all came on when the sun really started drilling here in CO, and I hadn’t really been riding earlier in the spring because of an injury. Sorry for the long post, just thought I’d share. Best of luck.
ERIK– I knew someone out there must have had the same issue with this sun block. Yeah… I actually used something else that wasn’t “waterproof” just “water resistant” and my skin seemed to do much better… no issues. Thanks for visiting and leaving a comment.