Anyone know what this is?

My son has had this on his back for like a month. He is prone to try skin and every time we take him to the doctor they say there isnt much we can do because he just has bad skin. So try switching laundry detergent, etc.

This doesn’t go away though no matter how many creams we put in it. Its a bunch of little red bumps and he scratches the area a lot.

Any ideas?