My father Is worried he has the measles, I am sure it is just Hives? Any Opinions??

My dad had a severe allergic reaction to Just for men Hair dye, his entire head and face got very swollen with pussing bumps all over his head, also a rash at the testin on his arm. He has been taking benydril for it and now it has almost completly gone, the swelling has almost completly gone down accept around his ears and his head has scabbed over, but is still a bit itchy. He ran out of Benydril yesterday and so he hasnt taken any since then. This morning he woke up and explained to me that he has little red bumps in welts up and down his arms, they are sortof itchy and are red. He explained it as red sorta blotchy- sorta bumpy kinda itchy rash up and down his arms. The worrier that he is, hes terrified he has the measles, but I am pretty much 100% positive it is just hives as a result of not taking the benydril and touching the other bumps from his head then touchin his arms. Any opinions on what it probably is, and what I can tell him to reasure him its not measles? =D