What Is The Itchy Rash On My Hands That Has Appeared Overnight?

hi there i was wondering about a rash i received on my hands and wrists this morning, i woke up and my hands felt a bit sore and a soon as i got into the shower a rash started to appear, its under the skin in red dots and is really itchy and sore. i haven't change any soaps or ate anything out of the regular and was wondering what it could be?