Originally Posted by
2manybikes
Sounds like something that happens to me once in a while. If I dress too warm on my legs and then ride anyway, I get what I think is a heat rash. It's red blotches, that look a little like a bruise. If I keep on riding it takes a long time to go away. I have arthritis in my knees and hips, and ankles etc. My joints feel good if I am dressed to keep my legs very warm, too warm for most people. I also wear long underwear under my jeans, this does not help either.
If I stay off the bike for two days and don't get too hot and sweaty, it goes away. It looks really terrible sometimes.
That happened to me once, and googling turned up "miliaria rubra".
I was descending from Echo Lake to Bergen Park and it was getting warm *fast* due to the time of day *and* because I was descending. I didn't pull off the heavy tights I was wearing over my shorts until I reached Bergen Park, and my legs were covered in a red rash, but were not painful. It took several days to go away.