Don't put sunscreen on babies under 6 months.

Basically no. Keep them out of the sun entirely. Sunscreen is not recommended for infants that young because their skin is too thin and absorbs chemicals more easily.

If shade, hats, and long sleeves aren’t an option (and you should try really hard to make them work), the AAP says you can use a tiny amount of mineral sunscreen (zinc oxide or titanium dioxide) on small areas like the back of the hands or face. Test a patch first. But the real answer is shade and avoiding peak sun.

This is one of those rules where the official guidance is actually right. Babies that small don’t need sunscreen — they need a canopy.