3 years of frustration, itchy red pimples, bumps, dryness, little red dots on arms.

3 years of frustration!! For 3 years since the beginning of my last year at high school (i am now 21)I have had small red dots on my arms (which are sometimes inflammed red), accompanied by small pimples and bumps, and occassional itchiness and dryness of the skin. I have tried many creams (including that proActiv stuff) to no avail, i have a fairly healthy diet and do regualr exercise, yet everything i have done hasn't removed it. This rash seems only to cover from the front and back of my left arm but not my bicep or inside of it. On my right arm it is less worse but the dryness and bumps are still there with some occassional redness. i don't know how this came about as i had none of this up to 3 years ago, my arms were clear. I don't know if its an allergy to laundry detergent or something i eat, or maybe rosacea, but i'm really getting down about it. Any help would be much appreciated. :)