Hives Before Bed

I was reading Owen a book around 7pm, and I noticed that he had some generalized itching on his face, neck, and back. At 7:30 he continued to have itching, and I noticed hives on his neck and back. I gave him benadryl.

I don't know what started the itching. He ate dinner at 5 pm. He was playing games at the dinner table, so maybe he contacted an allergen that way. I did wipe down the table after dinner. I just don't know.