Chronic spontaneous urticaria (CSU) is a condition in which you can develop itchy wheals and swelling under your skin that last for six weeks or less. These symptoms are driven by the mast cells in your body, as they are associated with the immune system and the body’s inflammatory response. One of the frustrating things about CSU is that you don’t always know what will trigger a flare. It can make living with the condition quite the minefield, and so that’s why many people try to find out as much as possible about potential triggers. Since CSU is essentially the body having an allergic reaction, it’s not unusual for people to ask if they should avoid certain foods. For some, the answer is to give the low-histamine diet a try. Is it the right move for you? Let’s find out a little more about it.
What Does Food Have to Do With CSU?
The answer, in part, lies with histamine. When triggered by an allergen, mast cells in your body release mediators such as histamine, proteases, and cytokines. These mediators then induce vasodilation, increase vascular permeability, and stimulate sensory nerve endings, leading to the swelling, redness, and itchiness characteristic of an allergic response. With that in mind, it’s not surprising that a few of the treatment options for CSU include second-generation H1 antihistamines and immunosuppressants.
When it comes to managing the condition, however, doctors also recommend avoiding triggers where possible. While triggers can vary from person to person, some common ones include nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin, opioids, alcohol, stress, sleep deprivation, fluctuations in sex hormones (eg, menstruation), exposure to cold or heat, and infections that can include vaccination.
When it comes to food, doctors have largely taken a personalized approach, allowing you to decide what to avoid if it causes a reaction. However, there has been talk of a low-histamine diet in which you actively avoid foods said to have high histamine content.
The diet was originally deemed helpful for people with histamine intolerance. This intolerance differs in that it refers to people who can’t effectively break down histamine. Typically, this is caused by low levels of diamine oxidase (DAO), an enzyme in the gut. When histamine builds up, you can experience a wide range of symptoms, including bloating, abdominal discomfort, gas, diarrhea or constipation, rhinitis, nasal congestion, sneezing, pruritus, flushing, urticaria, dermatitis, and swelling.
Given the role that histamines play in CSU, some people also wonder if a low-histamine diet would be helpful. According to a 2019 study, it’s rare for food to be a factor in CSU, but that depends on the individual. However, there are specific scenarios where it’s more likely to happen. For example, those with a history of tick bites, a history of raw or marinated fish ingestion, or living with celiac disease may have food-related triggers.
It was also noted that you may have a higher risk of a CSU flare if you’re already dealing with a food intolerance. When trials were conducted to compare pseudoallergen-free and low-histamine diets, a subset of patients experienced partial symptom remission. On the other hand, allowing them to consume foods that could potentially cause a flare confirmed that some patients showed worsening of symptoms after ingestion of food additives, tomatoes, herbs, seafood, alcohol, and other foods.
So what does that mean for you? Well, if you have food allergies or intolerances, it may be a good idea to check whether the foods that bother you also trigger CSU flares.
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Do You Have a Food Allergy or an Intolerance?
Researchers have delved into the links between CSU and food allergies as well as food intolerances, but what’s the difference? While both issues fall under a broad category of food hypersensitivity, there are differences in what causes them and the symptoms you’ll experience.
Food allergies come from an immune system’s response to protein in the food you’ve ingested. Although it can result from a variety of immunological pathways, the symptoms can affect several systems. You may experience sneezing, congestion, rhinorrhea, wheezing, throat swelling, nausea, vomiting, abdominal pain, diarrhea, urticaria, swelling under the skin, flushing, itchy skin, tachycardia, and hypotension.
With food allergies, you want to be on the lookout for a life-threatening condition known as anaphylaxis. This needs immediate medical attention as it can be fatal. Some symptoms include:
- Skin reactions, including hives and itching and flushed or pale skin
- Low blood pressure (hypotension)
- Constriction of the airways and a swollen tongue or throat, which can cause wheezing and trouble breathing
- A weak and rapid pulse
- Nausea, vomiting or diarrhea
- Dizziness or fainting
A food intolerance, on the other hand, is associated with your digestive system. It means that your body is unable to properly digest the food you’ve consumed. As a result, you may experience bloating, passing gas, nausea, and diarrhea.
You should note that it can take anywhere from a few minutes to two hours for symptoms to start. That’s why you need to take time to note changes after ingesting certain foods to determine if you’re allergic or intolerant.
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The Do’s and Don’ts of a Low-Histamine Diet
Now, you may be wondering which foods you should keep an eye on. That can be a tricky one to answer. A 2021 study that reviewed data on low-histamine diets found that the information wasn’t always definitive. Of the ten diet recommendations that were scrutinized, the only foods that consistently made the list were fermented. Although it would be more helpful to have a set list, the issue highlights why this kind of diet has to be highly personalized.
Still, there are a few foods that you can take a look at when it comes to your body’s reaction. These are:
- Aged or fermented foods (e.g., aged cheeses, kimchi, yogurt)
- Alcohol (especially wine and beer)
- Processed or preserved meats
- Certain fruits such as citrus, strawberries, pineapple
- Tomatoes, spinach, eggplant
- Vinegar-containing or pickled foods
- Chocolate
- Certain nuts such as walnuts, cashews, peanuts
- Leftovers stored for prolonged periods
Alternatively, there may be some low-histamine foods that you can safely include in your diet. Of course, it’s best to assess them just as much as the others regarded as high in histamine. You never know what may cause a reaction. This list includes:
- Gluten-free grains: rice, quinoa, millet, buckwheat
- Fresh (unprocessed) meats
- Fresh or flash-frozen fish
- Non-citrus fruits such as apples, blueberries, mangoes, peaches
- Non-dairy milk (almond, coconut, hemp)
- Most fresh vegetables (individual tolerance varies)
- Olive oil, coconut oil
- Seeds (flax, chia)
- Some dairy (if tolerated): fresh cheeses such as ricotta or mozzarella
How to Try The Diet Safely
Although it may seem easy to simply cut certain foods from your diet, it’s better to take things slowly. As noted previously, the results of the low-histamine diet’s effectiveness have been mixed and depend significantly on the individual. To ensure you’re safe, it’s best to talk to your doctor before making any changes. They can assess the likelihood that the diet will make a difference based on other aspects of your health.
If you’ve been given the ‘all-clear’ to try the diet, it’s a good idea to start by checking if you have a reaction to certain foods. When you’re living with CSU, it’s not always easy to know what triggered your flare. In this case, you’ll watch for any type of reaction after eating specific foods that have caused symptoms in others. The aim isn’t to eat more than you normally would to see if something will happen. You’re simply noting if there’s a reaction.
To get the best results, consider introducing different foods over a two- to three-week period while keeping a thorough food journal. You can then let your doctor know the results so they can help plot the way forward. It’s important to be deliberate about which foods you avoid because many of them aren’t inherently unhealthy. If you stop eating them, you may harm your health by not getting all the nutrients you need.
Even if you see that adopting a modified low-histamine diet can help manage your CSU, you have to keep a watchful eye on how it may affect other aspects of your health. For example, if you’re unintentionally losing weight or are tired all the time, it could be a sign that your diet isn’t balanced. At that point, you need to talk to your doctor about what you need to change.
It’s common to wonder if what you eat can be a CSU trigger. For some people, the answer can be ‘yes’. If you think a low-histamine diet may be worth exploring, talk to your doctor so they can detail the right steps to take. This kind of diet change isn’t one you want to rush.