Doctor's Notes on Hives and Angioedema
Hives and angioedema are reactions of the skin to histamine and other chemicals. Often, the release of these substances is due to an allergic reaction. However, there are many causes of hives and angioedema. Often, the specific cause cannot be determined, and the condition is termed idiopathic. Idiopathic hives and angioedema are very common. Common triggers of both hives and angioedema include infections, allergies, insect bites or stings, and blood transfusions.
Hives (medically known as urticaria) appear as wheals on the skin wheals that are smoothly elevated, red, very itchy patches of skin that often have a blanched center. Hives may be a few millimeters to several centimeters in diameter anywhere on the body and often form welts. Hives typically come one up suddenly often in several places. They may go away after a few hours and appear in another location on the body. Angioedema is like hives, only the welts are larger and form deeper in the skin, leading to severe swelling, usually in the face, near the eyes and mouth.
Hives and Angioedema Symptoms
Hives is a rash of smooth, raised, pink or reddish bumps of different sizes, called wheals. Hives appear suddenly. The wheals look somewhat like mosquito bites. They may cover all or part of the body and are usually very itchy.
- Hives usually break out first on the covered areas of the skin such as the trunk and upper parts of the arms and legs.
- Wheals appear in batches. Each wheal may last from a few minutes to six hours. As wheals disappear, new ones form. A case of hives usually lasts at most a few days.
- Hives are usually patchy at first, but the patches may run together until the hives cover most of the body.
- The patches can be small or large. They are usually irregular in shape. Often, the patches have clearing of the redness in the center with a red halo or flare at the edges.
- The itching is often very intense.
- Hives are characterized by blanching, which means that the redness goes away and the area turns pale when pressure is applied.
- Dermographism may be present. Dermographism refers to the appearance of reddened areas like hives that appear after light scratching of the skin.
Angioedema is related to hives but has a different appearance. Angioedema describes marked swelling, usually around the eyes and mouth. It may also involve the throat, tongue, hands, feet, and/or genitals.
- The skin may appear normal, without hives or other rash.
- The eyes may appear swollen shut.
- The swellings usually do not itch but may be painful or burning.
- The swellings may not be symmetrical (the same on both sides of the body).
- Like hives, the swelling of angioedema can go away on its own.
Other, more severe allergic reactions may occur with hives or angioedema. A reaction may start with hives or angioedema and then progress rapidly to more serious symptoms. The most serious allergic reactions, which can be life-threatening emergencies, are called anaphylactic reactions. The symptoms and signs of an anaphylactic reaction include the following:
- Swelling of the face, tongue, or throat
- Wheezing, a raspy sound when you breathe
- Difficulty breathing
- Difficulty swallowing
- Tightness in the throat or chest
- Rapid or irregular heartbeat
- Dizziness or faintness
- Loss of consciousness
- Respiratory stridor, to and fro breathing that is strained in the throat
- The dizziness, faintness, and loss of consciousness are caused by dangerously low blood pressure, also called shock.
Hives and Angioedema Causes
Hives and angioedema are reactions of the skin to histamine and other chemicals such as bradykinin, leukotriene C4, and prostaglandin D2. These chemicals act on blood vessels and other tissues to produce the clinical signs of hives and angioedema. This process is often, although not always, due to an allergic reaction.
There are many causes of hives and angioedema. At least half the time, the specific cause cannot be determined. When the cause of a medical condition is not known, it is termed idiopathic. Idiopathic hives and angioedema are very common.
Some of the more common triggers of hives and angioedema include the following:
- Infections such as viral illnesses, especially in children
- Allergies to food, medications, cosmetics, soaps, and detergents
- Insect bites and stings
- Transfusions of blood or blood products
- Emotional and physical stress
- Physical agents such as sunlight, heat, cold, water, or pressure
- Allergies to animals, such as pet dander
Chronic hives are hives that lasts longer than six weeks. This can happen to anyone, but it is most common in women who are 40-60 years of age. Chronic hives can last for months or even years, but this is unusual. Although anyone can get hives, some people are at greater risk.
Risk factors for hives and angioedema include the following:
- A previous case of hives or angioedema
- A previous allergic reaction
- Family members who have hives or angioedema
About one in every five people develops allergies. Allergies arise when the immune system overreacts to an otherwise harmless substance known as an allergen. That reaction can be as mild as a sneeze or as deadly as anaphylactic shock. The best way to reduce allergy symptoms is to avoid your allergens. So, what could you be allergic to?
Allergies : Symptoms & Home Remedies QuizQuestion
Allergies can best be described as:See Answer
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.