Food Allergy Hives (Urticaria)

A red, itchy rash could be a case of hives (urticaria).. Getty Images

You ate something and now you have a red, itchy rash. What's going on?

Hives, Defined

Hives, also known by its medical name urticaria, is a rash appearing as raised, red bumps that are often itchy. These bumps are surrounded by a red flattened area of various shapes and sizes and often occur over a large area. A related condition, called angioedema, causes swelling of the blood vessels under the skin and may result in pain and redness.


It’s estimated that about 15-20% of people will experience hives at some point in their lives. Mostly, hives are thought to be related to a food allergy or sensitivity with 63% of individuals who experience hives suspecting food as the trigger. Hives can be caused by both allergic or non-allergic triggers.

Types of Hives

Hives are categorized into 4 types:

  • Acute urticaria: Hives that last less than 6 weeks and are commonly caused by a food allergy, or in some cases, a viral infection (called viral exanthema)
  • Chronic urticaria: These hives last longer than 6 weeks and are rarely due to a food allergy. Rather, up to 30-40% of chronic hives are thought to be due to an autoimmune process.
  • Idiopathic urticaria: In this condition, the cause of hives is unknown, and the cause is identified in less than 20% of cases.
  • Cholinergic urticaria: These hives are caused by friction, pressure, extreme temperatures, exercise, and sweating.

    Hives can appear anywhere on the skin. A release of complex factors that cause inflammation (called inflammatory mediators), including histamine—the primary chemical responsible for the development of hives--come from the mast cells in the skin. Histamine may cause leakiness of the blood vessels, allowing fluid to leak into tissues and cause swelling (this is seen in the wheal).

    It may also cause widening of the blood vessels, increasing the blood flow and causing reddening. Lastly, intense itching caused by histamine occurs in the affected areas.

    Foods and other substances that are associated with hives include shellfish, nuts and medications. Inhaled allergens are thought to rarely cause hives. Specifically, shellfish, fish, egg, nuts, milk and wheat are frequently reported to induce hives. But, truly, any food is capable of triggering an allergic reaction in a sensitive person.

    Food Allergies Are Not The Only Cause Of Hives

    In addition to food allergies, some other causes of hives include medication or latex allergies, infections, exercise, heat, and cold. Hives can also appear for long periods of time and for no obvious cause, as outlined above.

    How Hives Are Treated

    The primary treatments for hives are antihistamines. Over-the-counter antihistamines, like Benadryl (diphenhydramine), are commonly used for short-term treatment of hives. Newer "second-generation" antihistamines, such as Xyzal (levocetirizine) and Clarinex (desloratadine), are often used because they tend to cause less drowsiness.

    In severe or prolonged cases, doctors may prescribe short courses of corticosteroids (such as cortisone or prednisone) to reduce inflammation. Epinephrine may also be used if acute hives are accompanied by symptoms of anaphylaxis.

    What To Do If You Suspect A Food Of Causing Hives

    Ask your doctor before you stop eating any food you're not sure you're allergic to. Your doctor may want to perform allergy testing before you eliminate foods from your diet. However, once the cause of your hives has been determined, avoiding the trigger food or non-food is an effective way to prevent further outbreaks.

    Home Treatment For Hives and When To Call a Doctor

    Uncomplicated hives over a small area of the body can be treated with over-the-counter antihistamines to help reduce swelling and itching. Hives that cover a large area of the body, appear after starting a new medicine or food, do not respond to over-the-counter antihistamines after several doses, or cause severe discomfort warrant a call to your doctor. Your doctor may want you to come in or may give you instructions for home treatment.

    Hives that are accompanied by breathing difficulty, changes in heart rate, or other symptoms of anaphylaxis are rare, but indicate an emergency. Call 911 or your local emergency number immediately and take epinephrine, if your allergist has prescribed it for you.


    Joneja, JV. The Health Professional’s Guide to Food Allergies and Intolerances.

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