Can you be allergic to CBD? Very uncommon, but possible. Also, you might have an allergic reaction to some other ingredient in CBD products, such as synthetic flavorings, preservatives, carrier oil, or other ingredients. When using CBD for the first time, it’s a good idea to apply a small amount to your skin first and check for allergies. If, after 30 minutes, you see no signs of redness or irritation, then your chances of having an allergic reaction are very low. Even if you use this test, it’s still a good idea to use a tiny amount of CBD the first time to see how your body reacts before moving to the full dose.