Urticaria and Angioedema (Hives and Swelling)

What are Urticaria and Angioedema (Hives and Swelling)?

Hives, or urticaria, are lesions occurring within the skin for a variety of reasons, both allergic and non-allergic.  They are a result of small blood vessels near the surface of the skin becoming “leaky”.  These leaky vessels can cause redness, as well as a collection of fluid, in the immediate area.  This results in a characteristic wheal (fluid) and flare (redness) reaction. 

Hives are typically very itchy, and can vary widely in size and shape.  They can occur anywhere on the body, and will clear without causing a change in the skin. 

Sometimes, hives will occur along with significant swelling, called angioedema, although angioedema can also occur by itself.  This reaction is similar to that of hives, but is happening at a deeper level within the skin, and is therefore usually not red.  Angioedema is generally also not as itchy, but can be painful.  It commonly occurs in the face, but can be found anywhere on the body. 

Both urticaria and angioedema are classified as either chronic, which last more than six weeks, or acute, which are present for less than six weeks. 

There are several different causes of urticaria and angioedema.  These can include:

  • Drugs: such as antibiotics, aspirin and other anti-inflammatory medications.
  • Foods: the majority of these cases involve peanuts, tree nuts, eggs, fish, shellfish, milk, wheat or soy.
  • Infections: including viral, bacterial, or parasitic.
  • Chronic disease: thyroid problems, chronic infections, autoimmune disorders.
  • Injections/Stings: especially from bees, wasps, and hornets
  • Physical: heat, cold, vibration, pressure, exertion.
  • Contact: latex, animal saliva, foods, among others.
  • Idiopathic: which is the most common type of hives seen, and generally has an uncertain cause.  

The most important part of evaluating urticaria and/or angioedema is to get a very thorough history from the patient, including past medical history as well as the course of the disease.  This is especially true of chronic urticaria and angioedema.   Physical examination is also vital, with special attention paid to the rash itself. 

Testing in patients with hives can be done by blood or with skin testing.  This can be an important step in evaluation not only to determine if there is an identifiable cause, but also to rule out other rashes that may appear similar. 

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