Allergic contact dermatitis is a Type IV hypersensitivity reaction, caused by a different immunologic mechanism than hives, angioedema, or anaphylaxis. However, very rarely, patients may have immunologic dysfunction which results in multiple types of concurrent hypersensitivity reactions. Thus, it is possible that people with contact dermatitis can develop hives (urticaria) and swelling (angioedema) after coming into contact with an allergen. Hives are red, raised, itchy skin welts. Angioedema is swelling deep under the skin.
Extremely rare, allergic contact dermatitis can overlap with a severe, life-threatening allergic reaction called anaphylaxis that can swell airways and close them. If you think you are experiencing anaphylaxis, call 911. You’ll need an immediate epinephrine injection to counteract this allergic response. People with known allergies can carry an EpiPen®, a brand of injectable epinephrine.