How do you protect a pizza peel?

I don't do anything for my peels. I only wash them if they get sauce on them, and then only with hot water and a gentle sponging. Never soak them with water. If you want to add a bit of water resistance, you could use some cutting board oil (a.k.a. mineral oil) to add some protection.

i use mineral oil, sometimes olive oil if i'm really out of everything else. if you happen to have an Ikea near you, a lifetime supply of mineral oil will cost you a couple bucks. i also clean it immediately after using it, so that nothing sits on the wood too long.

Wood is actually a pretty good bacterial inhibitor. Wood will last a long time - but not forever. We have a pizza peel that is 5 years old and it is used every day. It still is just fine without mineral oil or any other wood pampering.

Wood for culinary uses should be oiled with food grade vegetable oil

The olive oil from you pizza dough should be enough to keep it fine for many years

When not being used, make sure it is stored some where dark, dry, and not too warm. Make sure it is 100% clean and dry before you put it away

Mineral oil sold in a pharmacy is what you need. It is safe for human consumption (it's in the pharmacy because its a laxative) and does not go rancid.

Walnut oil does not go rancid. It dries fast and has been used for wood preservation since centuries. It's pretty expensive but hey, how much do you actually need?