Scratching a red rash like area only makes it worse. These links may help you figure out what's going on since there isn't a picture of your rash here. The first link has corresponding pictures of a particular rash and then gives possible causes, treatments, etc...
59 Possible Causes of a Rash
This link is from the NIH
Red, Itchy Rash?
Get the Skinny on Dermatitis
59 Possible Causes of a Rash
This link is from the NIH
Red, Itchy Rash?
Get the Skinny on Dermatitis