Major reactions: Red, bumpy or splotchy skin that feels itchy or painful. In this case, you should absolutely discontinue use and either discard the product or give it to a friend. You can treat the affected area with a soothing product, such as aloe vera or milk of magnesia. Mild reactions: You may also experience a mild reaction, which could mean one of two things. The first is that your skin isn’t fond of the product, so you should discontinue usage. The second scenario is that you’re using a product that causes an intended reaction. Products containing acids will do this — including lactic, salicylic, glycolic acids, hydroquinone and retinol. These reactions should be short-lived and will occur almost immediately after application, and last no longer than a half hour. If the reaction worsens over time or doesn’t get better within the half hour, discontinue use. If skin settles down within half hour, it should be okay for you to continue using the product. Normal reactions: If your skin doesn’t react at all, except to do what the product promises, then you’ve found the perfect match! Breakouts: Obviously, you want to keep an eye out for any new pimples, blackheads or whiteheads. These can usually be seen or felt, but you can also examine your skin with a magnifying mirror to determine if there are any clogged pores. If your skin is breaking out, it’s best to discontinue use.