# What is this rash? (with pictures!) **URL:** \ **Category:** In My Humble Opinion\ **Created:** [July 19, 2013, 7:11pm UTC](https://boards.straightdope.com/t/what-is-this-rash-with-pictures/663967 "2013-07-19T19:11:57Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![liirogue](https://avatars.discourse-cdn.com/v4/letter/l/dbc845/32.png) [@liirogue](https://boards.straightdope.com/u/liirogue)\ **Post date:** [July 19, 2013, 7:11pm UTC](https://boards.straightdope.com/t/what-is-this-rash-with-pictures/663967/1 "2013-07-19T19:11:57Z")
I’ve been riding my bicycle a lot, and whenever the temperature gets over about 90 degrees my legs start breaking out in a rash. The worst is on the tops of my thighs, but I will also get it on my calves and ankles. It’s red, puffy, and very sensitive. It extends about 3 inches above and below where my bike shorts hit on my leg. Ignore the gnarly tan line 😛 [Pic 1](http://i2.photobucket.com/albums/y48/liirogue/20130719_133419.jpg) [Pic 2](http://i2.photobucket.com/albums/y48/liirogue/20130719_133354.jpg) I’ve tried using different sun screen and different bike shorts, but the only thing that seems to make a difference is the temperature outside. Any ideas on what I can do to prevent it or treat it? ---
**Author:** ![Speak\_to\_me\_Maddie](https://avatars.discourse-cdn.com/v4/letter/s/58956e/32.png) [@Speak\_to\_me\_Maddie](https://boards.straightdope.com/u/Speak_to_me_Maddie)\ **Post date:** [July 19, 2013, 7:20pm UTC](https://boards.straightdope.com/t/what-is-this-rash-with-pictures/663967/2 "2013-07-19T19:20:29Z")
Looks like urticaria, aka hives. Some common causes are heat, moisture, irritation, excercise, etc. It’s an allergic reaction, but not always caused by allergens. I used to get them years ago on clothing contact points when exercising. The thing I found most helpful was putting a lotion containing dimethicone on those areas before working out, but it still didnt totally prevent it. ---
**Author:** ![liirogue](https://avatars.discourse-cdn.com/v4/letter/l/dbc845/32.png) [@liirogue](https://boards.straightdope.com/u/liirogue)\ **Post date:** [July 20, 2013, 3:43pm UTC](https://boards.straightdope.com/t/what-is-this-rash-with-pictures/663967/3 "2013-07-20T15:43:29Z")
Dang, **Speak** , looks like that’s what it is. Next time, could you diagnose me with something easier to treat? 😛 ---
**Author:** ![Turble](https://avatars.discourse-cdn.com/v4/letter/t/8dc957/32.png) [@Turble](https://boards.straightdope.com/u/Turble)\ **Post date:** [July 20, 2013, 4:55pm UTC](https://boards.straightdope.com/t/what-is-this-rash-with-pictures/663967/4 "2013-07-20T16:55:35Z")
You might try switching laundry products. I get hives around the underwear waistband from fabric softener dryer sheets. ---
**Author:** ![liirogue](https://avatars.discourse-cdn.com/v4/letter/l/dbc845/32.png) [@liirogue](https://boards.straightdope.com/u/liirogue)\ **Post date:** [July 20, 2013, 5:24pm UTC](https://boards.straightdope.com/t/what-is-this-rash-with-pictures/663967/5 "2013-07-20T17:24:07Z")
**Turble** , I considered that but I don’t use dyer sheets or fabric softener on my workout clothes. They air dry and I already use a hypoallergenic laundry soap. ---
**Author:** ![capybara](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/capybara/32/202_2.png) [@capybara](https://boards.straightdope.com/u/capybara)\ **Post date:** [July 20, 2013, 8:47pm UTC](https://boards.straightdope.com/t/what-is-this-rash-with-pictures/663967/6 "2013-07-20T20:47:21Z")
Try shorts without the elastic cuffs, or roll the elastic up over the lyrca a bit to see if it makes a difference? ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [July 20, 2013, 8:50pm UTC](https://boards.straightdope.com/t/what-is-this-rash-with-pictures/663967/7 "2013-07-20T20:50:52Z")
I vote for the laundry products. I switched to dash or all or even a baby diaper laundry soap. I think it has more to do with caustics than allergens. ---
**Author:** ![Girl\_From\_Mars](https://avatars.discourse-cdn.com/v4/letter/g/3da27b/32.png) [@Girl\_From\_Mars](https://boards.straightdope.com/u/Girl_From_Mars)\ **Post date:** [July 21, 2013, 5:15am UTC](https://boards.straightdope.com/t/what-is-this-rash-with-pictures/663967/8 "2013-07-21T05:15:20Z")
I used get something a little like that sometimes - contributing factors seem to be sun exposure (not always heat) and sunscreen - it’s only ever where the sun hits my skin - gets really hot and itchy, and it’s not sunburn. From what I’ve read some sunscreens contain chemicals that can cause photosensitivity and a rash when exposed to the sun. I changed my sunscreen to a more physical block and it’s been a few years since I last had it. Can’t be sure it’s the same thing, but could be worth considering. ---
**Author:** ![kayT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayt/32/3633_2.png) [@kayT](https://boards.straightdope.com/u/kayT)\ **Post date:** [July 21, 2013, 12:59pm UTC](https://boards.straightdope.com/t/what-is-this-rash-with-pictures/663967/9 "2013-07-21T12:59:32Z")
I’m allergic to all sunscreen and get hives just like that if I use it. ---
**Author:** ![liirogue](https://avatars.discourse-cdn.com/v4/letter/l/dbc845/32.png) [@liirogue](https://boards.straightdope.com/u/liirogue)\ **Post date:** [July 22, 2013, 10:25pm UTC](https://boards.straightdope.com/t/what-is-this-rash-with-pictures/663967/10 "2013-07-22T22:25:14Z")
I don’t think it’s caused by the laundry soap since it’s just on my legs, but I went ahead and bought some “all” brand to try on my workout clothes. We’ll see if it makes any difference this weekend!