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Leg rash and cycling pants

I'm having an ongoing problem with leg rash associated with cycling shorts.  The rash occurs on the front of my thighs, both above and below the leg bands.  I always wear sunscreen, and have recently tried Slide, purchased from our bike shop (it does not help).  The rash is bright red, blotchy, and does not itch, but feels like a sunburn.  Some of the areas are slightly raised, but no pustules form.  The rash is bright red the day after riding, then gradually fades over the next 4-7 days.   My family practitioner and dermatologist have looked at the rash soon after it appears, and have no idea what could be causing it.  I am not taking any medications that cause photosensitivity, and the rash does not occur on other parts of my body, or at any other time.  This problem first occurred when I was living in the upper midwest, and occurs now that I'm living in Florida.  
Any thoughts/ideas would be greatly appreciated!


This discussion is related to Rash Appeared on Legs.
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Avatar universal
No answers I'm afraid, but I have been getting a rash on the top of my thighs after my 50+ miles rides in warm weather ever since I switched from Pearl Izumi shorts, their low end version with silicon around the bottom of the leg to Louis Graneau shorts that don't have the silicon. . . go figure.  Both are Lycra and the Louis Graneau shorts seem to be higher quality and fit a bit tighter.  Last Sunday I had a first.  I rode just over 50 miles and it was getting hotter here in southern Arizona around 100 degrees and I rode in the afternoon, the hottest part of the day with hot winds, clear skies and on a section of bike path with no cool water available, only hot water from a couple fountains placed strategically in the direct sun so I didn't drink near enough water and was pretty dehydrated by the end.   After the ride I notice I had severe red rashes down both legs both under my shorts where I had them before but also down both calves with no fabric contact.  Going on four days now and the rash is beginning to fade.  It never itched but just felt uncomfortable or a bit tender like it had suffered a mild burn even though I had sunscreen on and did not get a sunburn, just this rash.  Very weird.
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Avatar universal
I have been riding for over 40 years without ever a rash.  Yesterday, I rode 37 miles in warm (80 degrees) sunny and  dry (I live in the desert) weather with some wind.  I wore Lycra Graneau shorts; shorts I had worn many times before.  I also had spread some sun screen that contained zinc oxide on my thighs.  I had this rash on the tops of both thighs when I returned.  Red with small bumps but no itch, no pain, just the rash.
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18626935 tn?1466434297
I have the same issue.  

It looks exactly like the pics posted earlier in this thread (which now spans back several years, it seems).  The red blotchy raised rash is related to longer rides (40+ miles) and only happens in hot weather.  Interestingly, if I wear full length cycling pants, it does not seem to happen.  It happens only with cycling shorts.  Most of my shorts use a silicon band (mentioned several times in the thread) at the bottom of the leg to help adhere them to the leg, so it might be related to the silicon.  I also use sun block lotion when using shorts that I do not use when using the full length cycling pants, so a reaction rooted in the lotion is possible.

But, I use the same lotion on lower legs and arms.  They are exposed to the same sunlight and same head.  But, the blotchy rash only appears on the top sides of the upper legs.  And, it never seems contact-connected to the cycling shorts or the silicon band - always appearing on the tops of the upper legs and always below, not at, the bottom of the shorts.

For me, it is mostly just unsightly, since it neither hurts nor itches.  My only adjustment has been to be less likely to revert to cycling shorts, even in hot SW Missouri and eastern Kansas summers.  

It seems likely some kind of allergic dermatitis, but prevention and treatment (to make it go away quickly) remain unknown.

So, it is linked to:
1.  Longer rides
2.  Hot weather
3.  It only happens when wearing shorts, but this may or may not be a direct link to the shorts themselves.

It may be (??) linked to [singularly or in combination]:
1.  Sunlight (this seems likely as some kind of necessary catalyst based on where the blotchy areas are located).  
2.  Sun block or sun screen lotion (or some ingredient) - but it is odd the areas are limited to the upper legs.
3.  Cycling shorts (or one of the elements used in their construction).  This would seem to be likely, since it only happens on my upper legs when wearing the shorts -- but (oddly) never shows up in the skin that is in direct contact with the shorts.  Some connection, but hard to understand what it is.

Any new insights or solutions would be helpful.

Tom Lawson
Webb City, Missouri
Trek 920 for mostly S24 road trips
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Avatar universal
I've got the same problem. I agree that it is something in the end of the pant leg , that leaches out with sweat. It reminds me of the allergic reaction I developed to my Fitbit last year. I wonder if I can coat my leg with something, like the zinc mentioned in another post up above, to prevent the exposure. I am also starting to develop some trouble with chlorhexidine soap products. I'll probably go ahead and have skin patch testing with tru test or something similar to try to figure out exactly what it is.
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Avatar universal
There is no doubt that it has something to do with the fabric. Perhaps my example of a rash with compression socks serves as a clue.  I refer to Compressport socks that are in most respects excellent and very effective guards that reduce calf fatigue.  However, they have an "enhancement" of 220 silicon gel buds surrounding the interior of the guard above the ankle.  Usually ankle length socks were worn beneath the guard, but one day I wore the guard beneath the socks and on that particular occasion I ended up with an irritating rash that was patterned precisely according to where the little gel buds were touching the skin.  Contact dermatitis.  Yes, as a previous post mentions allergy to silicon is rare, but it is not unheard of and can be acquired.  
One must hasten to add though, that the jury is still out on the silicon, it may be something to do with the chemistry of how the silicon is bonded to the fabric. Cycling shorts commonly use a very similar silicon to that of the compression socks precisely because the silicon enhances friction and prevents the cycling short material from riding up the leg and creasing uncomfortably.  It is possible for the rash to be exacerbated by heat and I doubt sun creams will do much to prevent it, posts above seem to confirm that.  I chanced upon this page because of a worry that what happened with my compression socks, might occur with cycling shorts.  Thanks to all who have written on this post to make me aware that there is indeed a problem.  I will prioritize searching for cycling shorts that do not use the silicon around the hem, but this is difficult, because so many do.  However, some brands are evolving towards use of a broad elastic band instead, that is what I will be aiming to purchase e.g. Castelli aero race bib shorts...now the world just needs an easy-to-find list of cycling shorts that do not use silicon!
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Avatar universal
I have exactly this problem when I ride my bike in the heat. I also get the same "rash" on the lower part of my legs on long walks/hikes in the heat. I once had it up my legs after walking a marathon route in the heat.
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Avatar universal
Theres a good chance that its the Lycra in the short. Have no none allergies ,went thought all the BS & came up clean. Started happening to me about a years ago at the 3hr part of my rides. Tried wearing Nike compression short under the bike shorts to minimize contact & I did have some success  
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Avatar universal
It is still a mystery to me.  I have continued to have the problem, regardless of what I have tried.  But..........perhaps a breakthrough!
This past week  I bought a pair of Pearl Izumi 3/4 tights, SPF 50.  They come to  just below the knee.  Although I've only had one ride wearing the tights, I am happy to report that the rash was in fact MUCH less severe than usual.  It was a hot sunny day, the ride length was my normal 30 miles on the same trail as in the past.  The only other difference was that I did not apply sunscreen on the thighs (covered areas).  I always apply sunscreen to all exposed areas, and do not experience the rash  anywhere else on the body.
I will let you know how future rides go!
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Avatar universal
Has anyone found out what this is?

I always thought it was an allergic reaction to the sun. I only seem to get it on hot sunny days (while cycling). I used to think it was when I didn't wear sunscreen but it also happens when I do.

Here's a pic after a long day with no sunscreen.

http://www.crazyguyonabike.com/doc/page/pic/?pic_id=663655

I also wear pearl Izumi with the grip rolled up.

My doctor once said it could be an allergic reaction to my sweat, don't know if I believe that because it only happens when cycling in the sun and heat.

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Avatar universal
Same thing is happening to me. Right below the cycling shorts. Been riding 200-300 miles per week in preparation for Ironman Florida and it pops up on long rides. Going to see a dermatologist if I can get in...
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Avatar universal
I have experienced the same thing on long/hot rides, with it getting worse the longer/hotter the ride.  At first I thought it was heat rash, but it doesn't resolve for a few days and looks more like an allergic reaction.  I have several pairs/brands of tri shorts and it happens with all of them.  Silicone allergy is extremely rare, but I wonder if it could be some kind of adhesive or additive (could there be any latex?).  REALLY hoping to figure out how to prevent this before my first ironman in August -- it will be HOT and I will be wearing the tri shorts for a long time!
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Avatar universal
I have just recently begun experiencing this same problem.  I just bought new bike shorts and the rash has been on both legs.  I am getting ready to go back to using my old shorts but, for anyone suffering from this, I have found that GoldBond powder clears it up almost completely the same day I have riden.
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Avatar universal
Could yours be an alergy to the sun lotion??
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Avatar universal
I have the same thing happening. It looks just like the picture in the 1st post.
EXCEPT, I do not wear biking shorts.
The first two times it happened I had street pants on (I'm not a serious cyclist) and then the 3rd time, I wore jean shorts.
There was NO material whatsoever in contact with the skin area that developed the rash.
After a 27 mile ride, there it was. I'd have to eliminate the chafing or allergen possibilities. What about vitamin deficiency?

I'd like to know more about the contact dermititis too. Does there have to be direct contact to the area?

I'm in FL, 90 degree weather.
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Avatar universal
I have the same problem, mostly on the inner thighs. It has become more noticeable since I started riding with new Sugoi bib shorts with the silicone band.  
One other thing I now realize, I use to ride wearing a nike swimsuit shorts under my bike pants (both the Pearl Izumis and the Sugois) and never had the rash then.  It has become moderate since I started riding "commando". :-)
I'm going to try riding with my nike swimsuit or compression shorts under again and report any changes.
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Avatar universal
Same thing happens to me and my Pearl Izumi's . I wonder if it has to do w the silicone 7 sunscreen combo? i put sunscreen on then my shorts, about mile 40 I noticed the rash appear. It appeared where the gripper is and then down the thigh to my knee.  Next week I hope I can remember to put on shorts, apply sunscreen and roll up the leg gripper...
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Avatar universal
Thanks BYKR4Acause
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Avatar universal
I am pretty new to cycling, but my last two rides of 50 miles and 60 miles I have come home with this same rash and it is so irritating.  You can't ride again for a few days because it looks so dang bad.  I visit my doctor in a few days who is a cyclist so I definatly be asking her opinion and I hope she has an answer.  If she does I will be sure to share it with you all!
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Avatar universal
Boy, I have exactly the same thing- top of thigh rash.  It happens with Pearl Izumi shorts.  Cycled the last couple of days with CEP triathlon shorts and no rash.  So, I'm convinced that it is something in the fabric of the Pearl Izumis that I am allergic to.
I sure wish a doctor would chime in on this thread.
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Avatar universal
Leg rash and cycling pants

I've tried taking some Zyrtec tablets (anti allergy) along with rubbing some zinc cream under the shorts, so that if the sun penetrates it, at least the zinc will block any burn that might occur.
I used Invisible Zinc so far..but I suppose the regular zinc might do just as good.

This is the best combination I've tried so far.

I did try using just the Invisible Zinc on its own without the Zyrtecs, but I did get a small amount of rash with that., so its BOTH for me in future.
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Avatar universal
I have this problem too, and if anyone knows a solution for it, please let us know here.

My rash is a bit prickly feeling, while I'm out on my bike (with the cycle pants and suncream (if I am wearing knee-length pants) but I also get it while I am wearing 'longs' over the top of my knee-length pants.



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Avatar universal
I have the EXACT same problem.  The longer the ride - the more the rash but - still - only on the top (front of the leg/thigh) and - never below the shorts.  No idea what's causing it.  It feels like a burn (as previously stated by others) but - it doesn't seem to bother me much after (no itching etc..).  I've put topical steriods on it - and - that seems to make it disappear quite quickly.  Given that there's so many people with this same issue - I'm surprised there isn't a 'oh - it's this' type of thing from one of the dr's.  It's strange to me that - if it was contact dermatitis - then - why is it only happening on the thigh area with people and - not the back of the leg as well...??
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Avatar universal
I'm so glad to have found this comments. I thought I was losing my mind.  I have the same symptons everyone else has and I can't figure out what is causing it.  I just went for a 50 mile ride yestreday and tried rolling up the band on my Pearl's and same old rash appeared!!  I just can't figure out what is causing it.  I'll be anxious to find out what Pearl has to say is in the material of the bands.  Although I tried wearing an old pair of shorts from 2 years ago last weekend and still experienced the same results. They also had a band along the bottom, but it did not look like the same material as was in my Pearl's.  I'm considering cutting the band out entirely to see what happens!!
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Avatar universal
I have the same issue... Last summer went on shorter rides and the rash would only go slightly above and below the band on both legs, but only in the front. Yesterday I went for a 70 mile ride and now have a rash 8" long on both fronts of my thighs. I wear the same shorts each time (washed in between, with Tide). I called Pearl Izumi today and they said that I could be allergic to the Silicon in the band- I'm waiting to hear back from them with a specific list of materials in those particular shorts. They suggested rolling the band up so there is no direct contact with the skin... I have a 100 mile fundraiser ride next weekend and I'm hoping that I can come up with something before then
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