You should still know what you are getting. If you are purchasing a specific product, it may because of (for example) a skin disorder and you know that specific

You should still know what you are getting. If you are purchasing a specific product, it may because of (for example) a skin disorder and you know that specific brand does not cause you any problems. There's also the question of how many corners are being cut - you can cut some and still get a safe, working (if inauthentic) product, but cutting too many (which a manufacturer of fake products is more likely to do) may result in a product which either doesn't work or is actively dangerous.