How can i tell the difference between sunburn and allergy?

Sun burn includes: S rash w red skin ; possible blisters, fatigue, fevers, chills or headache. Polymorphous light eruption(pmle) ; it has sxs that were just described as well as dense clusters of small bumps over the body w possible hives on legs/arms/chest. Solar urticaria (which is like a sensitivity) present w first set of symptoms as well as blisters, wheals ; possible dizziness, feeling faint ; confusion.