@strawCake - I don't think you necessarily always need to see a doctor for a skin issue. For example, I've had eczema before, and I don't need to see a doctor to know when I have it!
I think it's pretty easy to figure out if you're having a skin rash from an allergic reaction too. If you're itchy and puffy, you probably have an allergy. Most people can put two and two together. For instance, if you get a rash right after you switch laundry detergent brands, it's probably an allergy!