Itchy skin turns into fast spreading rash like bumps when scratched. both arms and right leg. do have allergies & asthma. not on meds for allergies.

Eczema: Usually an itch that turns to rash when scratched is eczema or atopic dermatitis. This is associated with allergies. Maybe start taking your allergy medications again.

Happy to help.: There are a couple of possibilities. First, dermatographism is a condition where scratching or marking the skin causes hives. Second, hives can arise without scratching as well. Antihistamines like Zyrtec/Allegra can help. If this persists, I'd recommend seeing an allergist who can allergy test you and help determine if other conditions are present.