Allergies to CBD are rare but not impossible. It’s also possible to experience allergic reactions from other ingredients in CBD products — such as carrier oil, synthetic flavorings, preservatives, or other ingredients. If you’re using CBD for the first time, it’s wise first to apply a small amount to the skin to check for allergies. If, after 30 minutes, there are no signs of redness or irritation, your chances of having an allergic reaction are very low.