Have you tried any of the anti-itch remedies like allergy medicine (Benadryl) or Calamine lotion?
If it is yeast, it usually has a speckled rash appearance, but not always. I have generally found a combination of Aquaphor (to hold it on the skin), Maalox (kills the acidity and skin breakdown) and antifungal cream (jock itch, vaginal infection or toenail fungus types all work) works pretty good on the kids.
Ichthyosis-en-Confetti Type 2
Husband, Nathan - 10, Elliot - 7, Oliver - 4, all affected.
I also have an unaffected daughter, age 8.
email: jennifer at confettiskin dot com
facebook - find me on "ichthyosis mommy spot" or "friends of ichthyosis"