The most common side effects of ENBREL are infections (like the common cold, sinusitis, and the flu) and injection site reactions. Injection site reactions have occurred, such as redness, itching, pain, swelling, bleeding, or bruising. These symptoms usually go away within 3 to 5 days. If you have pain, redness, or swelling around the injection site that does not go away or gets worse, call your healthcare provider.