Hi...a spread of rash from inner thighs to other body areas is a sign of poor immune response against a fungus. This can be treated by good hygiene measures like taking baths twice daily. Apply antifungal powders to the body folds to keep them dry.
Next Steps
in order for me to confirm the diagnosis and give you the right treatment, I shall have to see his photos. it will be a good idea to arrange a video consultation by contacting my clinic.
Health Tips
get him to sleep at 10pm. sit in direct sunlight between 7 and 8 am.