What Could Be Causing Your Hives?

There are many causes of hives including foods, drugs, infections, and diseases. Oddly enough, even though there are many potential causes, in the majority of cases of hives, the cause is unknown. Hives causes can be broken down into 3 broad groups:

  • Idiopathic: This means we don't know the cause; it just happens.
  • Immunological: Some hives are caused by changes in the immune system. A typical scenario would be coming in contact with something that causes cells in the immune system to trigger the release of histamine from certain white blood cells called mast cells.
  • Nonimmunological: Exposure to certain substances can cause the direct release of histamine from mast cells without the involvement of other parts of the immune system.

If you have hives, you want to know what causes them so you can eliminate that trigger and free yourself from the itching. The following lists are not exhaustive but do give the main known hives causes. While most cases of hives are idiopathic, see if you can eliminate any obvious causes of your hives. Just remember that it's best to talk to your healthcare provider before eliminating all possible hive triggers. If you suspect a medication is causing your hives, contact your healthcare provider immediately.

Hives Causes - Medications

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Many medications can cause hives, but only about 10% of hives are caused by medications. Hives will most often occur in the first 36 hours after starting the medication, but hives can occur even after taking a medicine for a long time. You can see that antibiotics are a common culprit.

Hives caused by the radiocontrast dye, codeine, morphine, and aspirin are usually not triggered by the immune system, rather these drugs cause the direct release of histamine from specialized white blood cells called mast cells.

Hives Causes - Diseases

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When a cause for hives can be found, it's most likely an infection. Viral upper respiratory infections cause about 40% of hives rashes. Fortunately, these hives outbreaks resolve as the infection resolves. A chronic bacterial infection, especially sinusitis, may be the culprit if a case of hives is lingering.

The diseases listed above are rare causes of hives, with the exception of thyroid disease. People with chronic urticaria have a higher incidence of thyroid problems compared to the general population.

Hives Causes - Foods

Image © Heather L. Brannon, MD

This list shows the foods that most often cause hives. But an allergy to foods is actually pretty rare, occurring in 1% of hives sufferers. Whether the food additives listed above actually cause hives is controversial. But many people think their hives are caused by food additives and want to try eliminating them.

Many people have a sensitivity to latex which causes a contact dermatitis. The foods listed in the second table above contain chemicals that are similar enough to those found in latex that eating them can cause an allergic reaction. If you have a latex allergy, cross these foods off your shopping list.


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