Urticaria: Hives and Weals

When most people think about allergic reactions, hives (also known as weals) come to mind. Urticaria is a vascular reaction within the skin. Smooth and slightly elevated red or skin-colored plaques or papules may erupt over widespread areas of the body. These hives tend to be intensely itchy and form in response to the release of circulating basophils and chemical mediators (histamine, cytokines, and platelet-activating factor) from mast tissue cells, which activate sensory nerves, resulting in blood vessel dilation and fluid leakage into local tissues.

Angioedema and Anaphylaxis With Allergic Reactions

In some cases, bradykinin is released, resulting in the formation of angioedema (giant hives). These large areas of rapid swelling include the lower layers of the skin and mucous membranes. Swelling may affect any area of the body, but the face, tongue, abdomen, larynx, and limbs are most commonly affected. If left untreated, cases of angioedema may lead to anaphylaxis, particularly when an allergic reaction is the causative factor.

Rapid Onset Urticaria: Viral and Bacterial Infections, Stings, & Allergies

Urticaria can have a sudden onset or become a chronic condition. In cases of acute urticaria, the causative agent may not be identified. Genetic mutations, as well as the immune and coagulation systems are involved in the process. Some of the following causes have been identified as inducers of rapid-onset urticaria and the formation of hives:

  • Viral Infections
  • Hepatitis
  • Upper Respiratory Infection
  • Mononucleosis
  • Mycoplasma
  • Bacterial Infections
  • Sinusitis
  • Dental Abscesses
  • Food Allergies (milk, peanut, egg, and shellfish)
  • Drug Allergies (antibiotics)
  • Vaccinations
  • Bee and Insect Stings

In some cases, widespread urticarial reactions have been linked to localized contact with agents such as latex rubber. Drug pseudoallergies are also known to occur, which cause urticaria without activation of the immune system. Some of the most common drug culprits include: radiocontrast media, opiates, NSAIDs, ACE inhibitors, and aspirin.

Chronic, Longterm Urticaria: Autoimmune Versus Inducible

Most causes of chronic urticaria remain unknown; however, in cases where long-term reactions have been investigated, autoimmune instigation seems likely. These include systemic lupus, thyroid disease, vitiligo, and celiac disease. In addition, chronic underlying bacterial and parasitic infections have been indicated. Although not caused by these agents, spontaneous cases seem to be aggravated by heat, tight clothing, viral infections, allergies, and pseudo-allergies. In contrast to chronic spontaneous urticaria, inducible urticaria develops as a direct result of exposure to a known physical stimulus. These may include: skin irritation, tight clothing, towel drying after hot showers, skin exposure to cold air or water, sweat from exercising, emotional upset, allergens, irritants, pressure on skin, sun or heat exposure, vibrations (jackhammer), and water exposure.

Allergy Testing to Determine the Cause of Hives

If a food or drug allergy is suspected as a cause of acute urticaria/hives, then skin prick tests, radioallergosorbent tests (RAST), or CAP fluoroimmunoassay may be performed. In cases of chronic spontaneous urticaria, the causative agent may be difficult to determine. Several modern and highly effective treatments are available for hives, weals, allergic reactions, and urticaria. When triggering factors are known, they should, of course, be avoided. Tight clothing should not be worn, foods and drugs known to cause reactions should not be consumed, one should dress appropriately for cold and windy weather, pressure points should be minimized, broad spectrum sunscreens should be applied prior to sun exposure, etc.

Contact Allegheny Advanced Dermatology Center to schedule an appointment. Call: (814) 944-7109.

In case of an emergency, contact 911 for emergency services.