How Do you know when/if you're alergic to a Facial Product?

A friend of mine was wondering how do you know if you're allergic to a acne face product like would it make you break out more or..How Do you know when/if you're alergic to a Facial Product?
you might experience a rash, break out, get hives, or other bumps your friend is right! But some acnee products might make you break out more before you get better! my friend told me about a product like that!How Do you know when/if you're alergic to a Facial Product?
If you get rashes... itching... abnormal breakouts... etc. test on a small area (like on your leg... see if the same things happen)
When u wanna try something new apply it in the leg or hend and wash it , after 24hrs if u have redness or any kind of trouble u should not use it, if everything is u can start using it
What you do when you buy a new facial product is to test it on the inside of your wrist. And if after an hour or two, your skin isn't irritated, then it's okay to use the product.
your face will swell up and get red. a common thing that people are alergic to is something peroxide. it's found in a lot of face stuff. my mom is allergic to it. it makes her super red and splotchy.
well, your face will break out more or get all red and dry....sometimes even itchy