Why should or shouldn't I peel button mushrooms?

The only motivation I'm aware of for peeling button mushrooms other than wanting a very clean, white appearance is to remove dirt, dust, grit, compost, etc. from the surface without the trouble of brushing or washing. It's arguably quicker to peel mushrooms than to brush them (though not in my experience) and many people don't like washing them because they absorb a little bit of the water, which is counter-productive when e.g. sauteing. However, peeling them means you are wasting some of your ingredients, and even a very dirty button mushroom is trivial to clean by washing or brushing.

I rarely find it necessary to clean supermarket mushrooms at all as they tend to be very clean on the shelf. If they're dusty, a gentle pat with a clean, damp sponge does the trick. I would advise against peeling unless you're going for a specific visual presentation that requires it.

See also: How to clean mushrooms?

I always peel my mushrooms if purchased from the bulk department. Just watch the other store patrons sneeze,cough, hack over the produce and you will become a peeler too.

I don't peel mine, or didn't until I found a "working woman" cookbook which used the stems & peels to make mushroom stock for soup the day after making grilled mushrooms. Aside from doing that, I've never done it. You need to be doing a lot of mushrooms to make this cost effective and I don't think mushrooms freeze well, so that's out.

It's my understanding that peeling mushrooms is like washing meat, advice previously given as a default and no longer viewd that way. Washing meat is considered dangerous now. I think that the mushroom thing is optional at this point, mostly I do NOT, unless I plan to make soup the next day!

Argument against one of the comments above: mushrooms can freeze well depending on the use afterwards. I wouldn't slice and freeze them to sauté later, they'd be mushy. However, I always cook with peeled caps, and save both stems and peels in the freezer to make broth later. They'll stay in the freezer for a long time and if they're just getting boiled and reduced down you don't need to worry about their texture.

I peel them specifically to build up my "stockpile" though. All the parts, cap, skin and stem, are good for cooking up. I just hate the idea of wasting caps in broth, so I set aside the not-as-desirable parts for that. I can cook a dish with just caps, but not with just stems and/or skins.

My mother is from England, growing up they used to forage for mushrooms. She was told to always peel them. I found on line the probable reason; there is a folklore that if you could peel the cap - it wasn't poisonous. BUT that is a myth! She still wants me to peel mushrooms, but since any mushrooms I use come from the supermarket :) , I decline, and she oftens picks them out of salads. If the mushrooms are cooked I can usually sneak them by her. She is now 97

I only peel my wild mushrooms if they say to peel them in the field guide, otherwise I leave them as is.

I peel mine, just the 1st outer layer as my mother did. Mushrooms grow in mold or manure so I really think one should peel and rinse them. I can't imagine wanting to eat mold or manure for health reasons

I work in a research lab as an undergraduate and our postdoc fellow has us peel mushrooms before we feed them to the flies. Apparently the skins can host nematodes, tiny roundworms, which can be bad for the flies. That’s why I peel my mushrooms now

I`m sure it might be a good idea if eating raw mushrooms. But I`m also sure that if cooking, all the germs and bad stuff will be killed and your mushrooms will be perfect and safe to eat.

I peel mine, because they’re grown in manure! As a health professional, I have an aversion to eating fecal matter, not to mention anything else that might be living in the manure, such as the nematodes mentioned below.

Yes wash mushrooms, you don’t want to eat bacteria or ringworms can be found on mushrooms. Also, you can’t just give them a quick rinse in plain water and expect the bacteria or ring worms on them to die. For gut safety just peel them and then give them a rinse in water.