Your child may just be thirsty! The first thing I do when I feel a headache coming on (which is almost never as I eat well and stay very hydrated) is drink at least one huge glass of water. It may take several glasses to catch up. If your pee isn't clear you are dehydrated. Often after sleeping all night is when we are most dehydrated. Please try this. I hope it helps!
YES, it works. May take a little while, maybe a couple hours for full recovery, and I also did some of the breathing exercises, but drinking water is well worth remembering to try! I realized after reading here that I had not drunk much water that day.