uggh... I have urticaria on the left side of my tummy.. and its no fun at all!
I agree it could be caused by something inhis room, if he wakes up worse than he was when he want to bed
some things to check
1. anything new or different he's had for dinner
2. new pillows, comforter, rug, or a different soap or detergent you have used
3. lotion, toothpaste
.. anything he has come in contact with before bedtime, or while he's asleep...