Is it unwise to swap shadows, i.e. might one engender infections, etc.? Also, how can one determine the age of a swapped product? Are there batch numbers, and if so, how do you read them?

Thanks

Nope. Powder doesn't hold germs like cream products do. So to swap/sell/buy a used powder product, like an eyeshadow, you would need to just wipe off the top layer with a cotton swap or tissue. if you really wanna get it totally clean, you could shave off the top layer with a sanitary tool, but that would leave the surface pretty uneven and unpleasing to the eye. but it works.
You can tell the age of a product by its batch number, which is usually found on the bottom of the item or on its box. For example, i have an eyeshadow numbered A65...it was made in 2005. the last digit of an item number indicates the year it was produced.

hope that helps!

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