I would try the cream on both of them. If it doesn't go away, check with a dermatologist.
My other concern is have you changed anything recently? Bath soap, laundry detergent, fabric softener. The only problem with that idea is that I would venture to think they would have this allergic reaction on their bodies too.
The last thought i have is scabies, but they are itchy.
http://www.mayoclinic.com/health/scabies/DS00451/DSECTION=2__________________