local rash on front of neck

hello just wanted to see if anyone can help me figure out why i have this extreamly itchy and painfull rash on my neck,,, i woke up this morning itching my neck in the throat region i though nothing of it unitl it persisted through out the day and increased pain and irration ! now its almost been 18 hrs since it started and i have taken a  oral anti-hystamine and applied a topical anit-itch cream on the effected area but it hurts even more!!!!!!!! I also have throat pain internally (if that make s a difference?)PLEASE SOMEONE HELP!