Anyway to stop TikTok purchases from the App store?

Hey, I'm looking for a way to stop a family member from purchasing Tiktok items. They enjoy looking on the app but as they've gotten older some mental issues have sprouted and they are in a loop of buying the same things from the app store on repeat and never using them. I desperately need a way to prevent the purchase of items on the app without stopping the use of its main feature.