Itchy Red Rash :(

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So yeah, i got this rash, and at the moment it spans lightly over my arms, but when it hits my collar bone it goes wild- front of my shoulders basically. I havent been scratching it because at the end of the day, ive taken allergy tablets to calm the itch. Im now out of them and am very tempted. It has been three days and it does not look any better... I was wondering if anyone thinks it may be stress related because i have been under alot of pressure lately... etc. No- I havent changed washing liquids or powders etc... so it is not to do with my clothes... any suggestion? It looks rather red and blotchy, a little like dry skin... but i have moisturised it too.. Help?