Just in case someday someone else would need to Google "Bikram yoga ear blisters," I'm going to tell this story.
A few weeks ago, my gf pointed out that I had a blister on the back of my right ear. Since it didn't itch or hurt, I hadn't realized it was even there. I forgot about it for a couple of weeks until I happened to see it in the mirror. Then I tried a hot compress, a sterilized needle, and various other things to get it to go away. No dice. In the meantime, I got a blister on the outside edge of my other ear. I'm not someone who's ever had skin sensitivities, contact dermatitis, or chemical allergies, so this was kind of strange. I hadn't changed soap, or gotten sunburned. The only thing I was doing was a lot of yoga, but I couldn't figure out how that would blister my ear.
And then, after a couple days of thinking about this, I got the bright idea to take out my earrings. The same little silver earrings I've worn for years. And within a day, the blisters were clearing up -- and so was my face, which had been unusually splotchy and irritated. Within three days all was clear. The problem? I seem to have developed a nickel sensitivity induced by sweating while wearing earrings. Silver earrings, (and in fact, almost all gold earrings, too) contain small amounts of nickel (the metal most people with such sensitivities react to). Sweat releases the nickel from the metal and often creates skin reactions. With the rise of body piercing among Westerners, nickel sensitivity is increasing too. The EU has recently issued guidelines for the reduction of nickel in jewelry for pierced wear, and has been performing tests with artificial sweat on the new euro coins to determine the potential public health issues.
So: if you're exercising a lot, do yourself a favor and take out your earrings. I had no idea that after 28 years of pierced ears I could develop a problem. And since my ear piercings themselves weren't affected, it took me a long time to figure it out. In hindsight, I now see that my skin was showing the reaction elsewhere on my face and neck, but I wasn't concerned enough about it to really pay attention. I just figured it was part of the hormonal weirdness of nearing 40.