Poison Oak
When mountain biking, especially in the bay area, you will eventually come across poison oak. You can't avoid, and for those who have never been a victim of poison oak, don't believe that you are immune to it. The more you're around poison oak, the more susceptible you will be!
There are many products out there that are supposidly block you from getting poison oak or help you treat or mitigate its effect after exposure, but nothing is full proof.
So you took a cold shower and scrubbed well with soap after your exposure to poison oak on the trails, and you made sure you washed your cycling clothes and didn't touch you skin with your nasty gloves that might have poison oak on it, but this might not be enough.
Usually, 2 to 4 days after being around this nasty stuff, if you got it, you will see little bumps on your skin like bug bites, but usually they will be close together, possibly like in a line formation. As the days progress, they will start to blister and ooze and itch uncontrollably.
Tecnu is a good product on the market that you can use to wash the oak off of you once you're exposed to it, however once the poison oak has taken affect on your skin, you just need to wait it out. It can take several weeks before it clears up. After you know the poison oak oils are gone from your skin, a great way to relieve the itching is to run hot water on the poison oak area. The infected area will turn white and start to feel really good after a while. I do this for about a few minutes and the itch goes away for the rest of the day.