Margaret,
The carbonation of the gingerale is likely getting underneath the dead skin cells and pushing them free. Unless this results in pain just consider it a normal part of the healing acclerated by carbonation.

As for my previous post,
You can eliminate the lemon juice and eliminate or significantly reduce the salt content until he can tolerate it. Everything is trial and error and different for every patient.

Just keep trying different things and know we are here for you and praying for you.

Good Luck
Mike