Lice!?!?

De

My sister came over, and then found out later that night her kids had lice. My son was playing with her daughters hats. He has been crying for the past three days and scratching his head. He has a rash on the nape of his neck and a few zit looking spots on his scalp. He is super light blonde. I can’t see anything in his hair.

What do I do!?