The FDA issued a warning about the use of topical creams and gel pain relievers as new evidence suggest that topical analgesic irritation can be extreme in a small number of people. This could include an intense burning sensation which could also lead to blistering and a skin rash.
Seek medical attention if this happens to you and remember to always use common sense by not using these types of skins on broken or already irritated skin. If you have not used this medication in the past, you might also want to apply it to just a small portion of your skin first to make sure no problems arise.
Of course in my case I will also have to exercise a bit first to have to worry about sore muscles.