Yes, it is possible to be allergic to Christmas trees. Christmas tree allergies are caused by the release of small amounts of pollen or tiny particles from the tree that can trigger allergic reactions in some people. These allergens can cause symptoms such as itching, sneezing, nasal congestion, and red, itchy, watery eyes. In rare cases, severe reactions such as difficulty breathing can occur. If you are experiencing any symptoms after being around a Christmas tree, it may be worth consulting with an allergist to determine the cause.