Hello everyone! My son is 8 months old and he's allergic. He has red c…

Hello everyone! My son is 8 months old and he's allergic. He has red cheeks constantly and scratches his head. It's impossible to take off his hat. We live with my husband's parents, his grandfather bathes him with household soap, although I told her that it contains alkali and it can't be bathed in. And she does what she wants directly. Every time I get angry at her, I don't want to offend her. But then she gets upset and stops talking to me, pretending that I am bad and not giving the child. Although the child is always with her even if the son cannot be in the sun, she still goes out into the sun. How should I act with her anyway