I really don't understand if I should or should not be using undershirts?
On one hand it feels like an extra piece of clothing that you have to put up with (buy, change everyday and wash), but on the other hand having something that sits between your main clothes feels cleaner.

>>18486493 (OP)
Wear undershirts when appropriate. Don't wear undershirts when they are unnecessary.
You don't need an undershirt under a T-shirt or polo.

>>18486494
>You don't need an undershirt under a T-shirt or polo.
Yeah, no shit about that.

>>18486493 (OP)
It is better to wear one if you live in a hot (non-humid) climate. It will absorb all the sweat and keep your actual shirt clean. And don't get those t-shirt style loose undershirts but form fitting ones. They'll also make your shirt drape much better on your body, instead of making it cling to your skin everywhere.

>>18486493 (OP)
>change everyday and wash
as opposed to changing the shirt every day and washing it?
as >>18486501 said, it keeps your actual shirts clean for longer so it has a proper function that for many is very handy

>>18486501
>wear two shirts in summer
>Sweat 10x harder
???

>>18487009
You're going to sweat either way, and you're not going to sweat 10 times harder. The difference is negligible, especially if you're not living in a humid place. So it's better to sweat into an undershirt than your actual shirt. It's especially useful with dress shirts, which aren't supposed to be washed after every single wear because it will destroy them.

>>18486493 (OP)
I wear them in winter, lets me wear my shirts more than once, and it's an extra layer for warmth, and it feels comfortable. In summer I wear my short sleeve shirts solo and that's the least hot thing I can wear, I have to wash them each time. I can't wait for the cool weather to come back.

>>18486493 (OP)
Only time I ever wear an undershirt is if I'm wearing a dress shirt and don't want my nipples to show