Hives, also known as urticaria, affect about 20% of people sometime in their life. They appear as raised itchy bumps caused by small blood vessel leaking when the immune system releases histamine. There are two kinds of hives, acute and chronic. Acute hives occur after coming in contact with a particular trigger: food, insect sting, medication, latex, infection, pet dander, pollen or plants (i.e. poison ivy). It can also be triggered by non-allergic causes such as heat, cold, pressure or exercise. Chronic hives, on the other hand, are rarely caused by specific outside triggers. They can be frustrating lasting months to years and allergy testing is usually not helpful. With the approval of Xolair (Omalizumab) in 2014, patients now have a fast and very well tolerated option for treating chronic hives replacing high dose antihistamines (that can be sedating) or other more toxic therapies (cyclosporine or steroids).
Swelling in deep layers of the skin is called angioedema. It is often seen together with urticaria. Acute angioedema is commonly caused by an allergic reaction to foods, insect stings or medications. Chronic recurrent angioedema, just like chronic urticaria, typically does not have an identifiable cause.
Hereditary angiodema (HAE) is caused by a deficient or improperly functioning protein called the C1 inhibitor. HAE is a rare but serious condition that usually runs in the families. It causes rapid swelling (without itching or hives) particularly of the face and airway. Evaluation by an allergist is critical as preventative and acute treatments are available.