Thanks for the query.
He might be suffering from atopic dermatitis
It is a chronic allergic condition.
Try to use plain petroleum jelly.
It is most non irritating thing.
He should get relief with this.
Also it will form a barrier so any chemicals wont come in contact with his skin.
Please meet a dermatologist
and discuss regarding this.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.