Itchy Red Rash?!

Itchy Red Rash?

I have developed a splotchy red semi-raised rash extending from under my forearm up under my bicep area and also behind my knees. The itching is mild. I have a taken Benadryl tablet by mouth and also tried their topical itch cream.
I havent changed my diet, food or laundry soap. What the heck could this be? No fever either. I havent passed it to my newborn or my husband, neither of them have it.

How can I have an alergic reaction to something if nothing new was introduced?

Any ideas?

without knowing how long u have had the rash i would say it is a heat rash. it usually occurs in hot spots of the body, behind the knees, underarms, waist, to treat this when my hubby had it, i had him wear loose fitting clothing especially to bed and i covered all the rash area with plain old baby powder, seeing as the powder will help absorb moisture. hope this helps.