About 20 percent of the population has experienced at least one episode of hives. For some, hives are just a part of life, requiring constant vigilance to avoid food and environmental triggers or diligence in controlling underlying health issues. For an unlucky few – about two to three percent of people – hives are idiopathic, with no known cause. They may even be caused by stress.
Although hives aren't difficult to identify, figuring out what's causing them is sometimes easier said than done, according to Connie Hsu, MD, an allergy/immunology physician on staff at HonorHealth John C. Lincoln Medical Center.
Clinically known as urticaria, hives occur when the immune system releases the compound histamine in response to an injury, infection or allergic reaction. Hives generally appear like a rash of itchy, round, red, and sometimes raised, bumps or welts on the skin. The welts can vary in size. They sometimes merge into plaques and typically last for hours but sometimes for days. Treatment requires determining whether the outbreak is an acute, sudden episode or a recurring, chronic condition.
What are common causes of hives?
Hives often are caused by an allergic reaction to a food, environmental allergen or chemical. Even common non-steroidal medications like aspirin and ibuprofen can cause them, and so can infection.
Hives that last longer than six weeks or with recurring outbreaks over a six-week period are most commonly caused by viral or bacterial infections like Helicobacter pylori (bacteria in the stomach), hepatitis or a dental infection. Autoimmune diseases like lupus and Hashimoto disease can also cause hives. While rare, hives have been associated with cancer. In children, the most common cause is infection such as strep throat or acute viral syndrome.
Dr. Hsu says fresh fruits and vegetables tend to be more problematic for those with pollen allergies due to a condition called food-pollen syndrome, which is a cross-reaction between pollens and certain fresh fruits and vegetables. She says cooking produce can destroy the heat-sensitive antigens, minimizing the risk of allergic reaction. Other foods that top the allergy list include:
- Milk and dairy products.
- Tree nuts.
Depending on the person and the allergen, consuming these foods can cause an allergic reaction, including hives. More severe cases may result in anaphylaxis, a life-threatening allergic reaction requiring medical attention.
What are environmental triggers for hives?
Arizona is an allergy hotspot thanks to its near-constant sunshine, mix of native and non-native plants and trees, and lack of freezing winters that has plants blooming throughout the year. Dr. Hsu says photosensitivity, a skin reaction to sunlight, is also known to cause hives. Other causes such as ice, hot showers or pressure on the skin from things like tight, restrictive clothing, can lead to hives. So can pollution and different types of airborne allergens, including dust or even dry mold that gets released into the air during construction. Airborne allergens are among the most troublesome because you can’t avoid them.
How do you treat hives?
Dr. Hsu says blood and skin tests may be necessary to determine what you’re allergic to and, in turn, what may be causing your hives. Generally speaking, hives alone aren’t dangerous, and they can usually be treated with over-the-counter antihistamines such as Benadryl. However, if hives present as part of systemic allergic reaction, seek immediate medical attention. More severe cases of hives or those that are idiopathic require a second line of defense with prescription medications.