Sit them down and tell them exactly that - it makes you feel anxious and unwell, and you prefer xyz gifts. Explain it exactly like you did to us, emphasizing that you know they just want to show their love but it's just causing you anxiety and makes it hard to clean. Do it in private with everyone one on one, so they don't get defensive out of embarrassment and dig their heels in.
I had the same problem with my parents, but manifested slightly differently.
My parents are from the Balkans, and our culture puts lots of importance on being a good host. So, whenever I visit my home country, my mom and dad buy several kg worth of meat for one meal, dozens of donuts for me to eat for breakfast alone
, a variety of pastries and cakes so i can just choose "which ones I like", and it's like that for weeks until I leave. It results in crazy amounts of food waste and they're just pissing away money that they don't really have a lot of.
I had to confront them about it and they got mad when I wasn't eating because "But we bought that just for you! Be grateful and eat it!". It took lots and lots of emphasizing that it makes me feel really bad to make them stop, but they did.