“Chronic idiopathic urticaria (CIU)” is the term for hives that last at least 6 weeks and have no known underlying cause. Learn how reducing histamines in your diet may help improve symptoms.

Many people think that hives are always an allergic reaction to something specific. This isn’t the case with chronic idiopathic urticaria (CIU).

“CIU” is the medical term for hives that last 6 weeks or more with no known underlying cause. Experts believe autoimmune dysfunction may play a role.

Symptoms can come and go for months or even years. A variety of factors can make the condition worse, including:

  • exercise
  • stress
  • heat
  • cold
  • pressure
  • infections

Hives can also appear spontaneously, prompted by what seems like nothing at all.

Even though CIU isn’t an allergic reaction, adjusting your diet may provide symptom relief.

At the moment, there’s not much concrete evidence about the effects of particular diets on CIU symptoms. Still, some limited trials show that dietary changes may help relieve symptoms, at least on an individual level.

Here are some possible diets and foods that may help you manage your CIU symptoms.

High levels of histamine may play a significant role in CIU since many people with the condition respond well to antihistamine medications.

For people who don’t respond well to antihistamine medications, trying a low histamine diet may be worthwhile.

In a small 2018 study, 22 people with chronic urticaria restricted histamine-rich foods for 4 weeks. There was a statistically significant decrease in participants’ urticaria severity scores.

Blood samples from people in the study also showed that the level of histamines in their blood had decreased after 4 weeks on the low histamine diet.

The following foods are low in histamines and may help you manage your CIU symptoms:

  • most vegetables
  • fresh meat
  • certain varieties of fresh fish, including salmon, cod, and trout
  • dairy products other than cheese and yogurt
  • bread
  • pasta
  • rice

You may want to consider avoiding or limiting the following foods that are high in histamines:

  • spinach, tomatoes, and eggplant
  • fruits, such as strawberries and cherries
  • preserved meats
  • canned, frozen, and smoked fish, including tuna, anchovies, and sardines
  • cheese
  • yogurt
  • fermented foods
  • fast food
  • seasonings, such as chili powder, cinnamon, cloves, and vinegar
  • alcoholic beverages

This list isn’t exhaustive. The amount of histamine from dietary sources can vary.

Some foods, beverages, substances, and medications are also theorized to either help in the release of histamine or inhibit the enzymes needed to break it down. A few examples of these include:

  • citrus fruits
  • papaya
  • pineapple
  • nuts
  • egg whites
  • alcoholic beverages
  • tea
  • food additives, such as certain preservatives
  • nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin
  • antibiotics, such as isoniazid and doxycycline (Monodox, Oracea, Vibramycin)

There’s little evidence to support this theory, though, according to a 2021 study.

Even if a person tests negative for food allergies, it’s possible they may have a hypersensitivity to or intolerance of certain foods. Eating these pseudoallergens can result in reactions that resemble a true allergic reaction, including hives.

With this in mind, some doctors may recommend that people with CIU try a pseudoallergen elimination diet. This involves avoiding certain potential pseudoallergens for several weeks and slowly reintroducing them.

Some examples of pseudoallergens include:

  • histamine
  • food additives
  • natural substances in fruits, spices, and vegetables

In a 2010 study of a type of CIU called chronic spontaneous urticaria, approximately 1 in 3 participants responded positively to a pseudoallergen-free diet lasting 3 weeks.

However, there haven’t been any randomized controlled trials to draw conclusive evidence about the diet’s effectiveness on a greater scale.

In fact, in 2014, the Joint Task Force on Practice Parameters recommended against a pseudoallergen-free diet for chronic urticaria. The expert panel comprises representatives from the:

  • American Academy of Allergy, Asthma & Immunology (AAAAI)
  • American College of Allergy, Asthma & Immunology (ACAAI)
  • Joint Council of Allergy, Asthma & Immunology

If you think your diet plays a role in your CIU symptoms, talk with a doctor about your options.

A doctor can help you figure out which foods and beverages to safely remove from your diet. A person’s tolerance for histamine is unique, so it’s very important to create an individualized diet plan.

You might also find it useful to track your symptoms in a journal after each meal. Take notes that include:

  • the specific foods you ate
  • what time you ate them
  • whether your symptoms got worse or better after eating (and how long it took for you to notice)

Share your findings with the doctor so you can work out a plan together.

Everyone reacts to foods differently. One type of diet may work for someone else, but it may not work for you. Before trying a new diet, talk with a doctor. They can help you understand what to do based on your personal circumstances.

There’s still not much evidence that adopting certain diets can consistently and significantly affect your CIU symptoms. However, the low risk and low cost of doing so can make dietary changes worth a try.