Hives (Urticaria) are those itchy, pink to red, raised skin lesions that are surrounded by a red halo. Although somewhere in the range of 90% of anaphylactic reactions are accompanied by urticaria or some sort of skin reaction, there are many other non-allergic causes. Some of these include physical factors (e.g., pressure, cold), infections (viral, bacterial and parasitic) and systemic illnesses. With all of these possibilities, it is not unusual when no cause is found.
So, question (but don’t exclude), the diagnosis of anaphylaxis when there is no sign of skin involvement. Conversely, don’t jump for the epinephrine when an urticarial eruption is the only finding.