Your gut health is intricately connected to both seasonal allergies and food allergies.
The strength of this connection is likely because the largest density of immune cells in the body is in the small intestine.
Research shows that probiotics can significantly improve seasonal allergy symptoms.
Elimination diets can also help to improve allergy symptoms (including environmental allergies).
The connection between gut health and allergies, whether they’re food allergies or seasonal/environmental allergies, starts with the immune system. The immune system dictates whether the body needs to defend itself against certain foods or environmental substances.
When the immune system decides it needs to protect the body from a “harmless” substance, like lactose, pollen, or another environmental agent, we experience allergy symptoms. We may be exposed to some of these allergens in the air or through the sinuses, lungs, and skin. But we’re also exposed to many allergens through what we eat and drink. This is where the gut gets involved in allergic responses.
The largest density of immune cells in the body is in the small intestine — this is likely why the gastrointestinal tract has such a huge impact on the immune system and allergies.
Fortunately, this connection tells us where to target therapies for reducing allergy symptoms. Through strategies like elimination diets and probiotics, we have the opportunity to fortify the gut and the immune system to reduce allergy symptoms and regulate the immune response.
Defining Allergies, Sensitivities, and Intolerances
Allergies are an inappropriate and immediate immune response to foreign substances (known as antigens or allergens) that are typically harmless to the human body . Allergic reactions usually occur in areas of the body that come into direct contact with an allergen . For example, foods can cause swelling in the mouth, pollen in the sinuses can cause a runny nose, etc.
Common allergic responses include:
Anaphylaxis: A sudden and severe allergic reaction that constricts the airway and therefore can be life-threatening . It typically happens with foods, medications, insect stings, and allergen immunotherapies. For example, a peanut allergy may produce this response.
Allergic rhinitis (hay fever/seasonal allergies): Symptoms usually include runny nose, nasal congestion, sneezing, watery or itchy or red eyes, and nasal itching 
Food allergens: The most common problematic foods include milk, eggs, peanut, shellfish, wheat, and nuts .
House dust mites
Venom in insect stings and bites
Contact allergens such as metals or fragrance ingredients
Sensitivities, typically food sensitivities, also come from an immune response like allergies, but unlike allergies their symptoms are usually more vague and may even be delayed by hours. (Remember, allergic reactions are usually immediate and happen with direct contact to an antigen.)
Symptoms of sensitivities may include:
Joint or muscle pain
Common food sensitivities include gluten, dairy, soy, nightshade veggies like eggplant and tomatoes, and eggs. But a highly sensitized immune system can develop a sensitivity to just about any food, which may lead to more and more restrictive diets. It’s likely that food sensitivities develop from a leaky gut or inflammation from overgrowth of gut microbes, leading to immune system dysfunction.
Intolerances, unlike allergies and sensitivities, are not caused by an immune reaction. Instead, intolerances are caused by an insufficiency or defect in certain enzymes needed to break down a specific food or nutrient.
So lactose intolerance, for example, is caused by a lack of the enzymes needed to digest lactose. Histamine intoleranceis generally caused by a deficiency of the enzyme needed (diamine oxidase or DAO) to break down histamine in the body. A buildup of histamine can manifest as symptoms that feel like seasonal allergies, but without the allergen present.
Whether you’re dealing with allergies, sensitivities, or an intolerance, you can start to look at your gut health to identify how it may be contributing to your symptoms.
Food Allergies and Gut Health
Perhaps it’s unsurprising that there’s a connection between gut health and allergies to foods due to the significant presence of immune cells in the small intestine. Research shows that the following issues related to gut health may be connected to the development of allergies:
Immune system dysregulation in the intestines [7, 8, 9, 10]
Gut infections (microbes such as parasites, candida overgrowth, etc.) 
Infant dysbiosis may relate to childhood food allergies [24, 25, 26]
A key link to developing food allergies seems to be a decline in the health of the microbiome (our community of healthy gut bacteria in the colon). A literature review attempted to highlight the role of the microbiome in allergic diseases. The review found that infants with allergic diseases, including food allergy, atopic dermatitis (eczema), and asthma, have been shown to have reduced levels of healthyspecies of bacteria and elevated levels of pathogenic bacteria in the gut .
Another literature review explored the role of the gut microbiota in food allergies and found that dysbiosis likely precedes food allergies. In fact, some research showed that improving gut health with probiotics may help to promote earlier resolution of food allergies in young children .
Seasonal Allergies and Gut Health
Making the connection between gut health and food allergies is a logical jump, but it turns out that gut health has a lot to do with seasonal and environmental allergies too.
Seasonal allergies also correlate closely with dysbiosis in both children and adults. Adults with seasonal allergies have also been shown to have lower levels of butyrate-producing bacteria  compared to healthy controls. Additionally, children with high levels of butyrate have been shown to have a reduced risk of developing allergies later in life .
Several GI disorders are associated with an increased risk of having seasonal allergies and other allergic conditions. IBS, functional dyspepsia, and constipation were associated with increased odds of having seasonal allergies, eczema, and asthma in one study .
Similarly, another study found that people with seasonal allergies and asthma were more likely to have GI symptoms compared to people with other chronic diseases and the general population . Other gut conditions associated with seasonal allergies include inflammatory bowel disease , GERD, gastritis, peptic ulcers, IBS, functional GI disease, gastroenteritis, colitis, and/or constipation .
How to Use an Elimination Diet for Gut Health and Allergies
Whether you have obvious gut symptoms alongside your allergies or not, it may be helpful to do an elimination diet to identify any foods that may be triggering your symptoms. Research shows that people who go on elimination diets of various kinds (depending on their food triggers) have improved allergy symptoms.
Elimination diets also tend to be the best way to identify food sensitivities, such as non-celiac gluten sensitivity, since testing can be unreliable.
Here is the general process we recommend to patients for starting an elimination diet.
Step 1: Cut Out Added Sugar &Processed Foods
This step eliminates a lot of added sugar, processed or trans fats and oils, and processed carbs, grains, and proteins. Replace processed foods with whole, fresh foods, making sure to meet your required nutrient intake.
For some people, this step alone is enough to resolve many of their symptoms. But if this isn’t enough, you can move on to step 2.
Step 2: Try a Paleo Diet
Paleo is the anti-inflammatory therapeutic diet we typically recommend to our patients when first starting to heal their digestion and lower systemic inflammation. Paleo prioritizes whole, fresh foods, including fruits and vegetables (lots of prebiotics), animal proteins, and some starchy vegetables. It eliminates dairy, grains (and therefore, gluten), processed foods, alcohol, soy, beans/legumes, most processed vegetable oils, and artificial sweeteners.
Some people can do a modified version of Paleo that includes some non-gluten grains like oats and rice, especially if they find they need extra carbs to maintain their energy levels. But some do very well on the no-grain version.
If your symptoms resolve on the Paleo diet after a few weeks, you can try adding certain foods back into your diet to see whether they trigger any symptoms. It’s important to reintroduce foods one at a time and monitor how you feel for a few days before moving on to another reintroduction.
But if Paleo doesn’t resolve your symptoms, you can move on to step 3.
Step 3: Try a More Specific Elimination Diet Such as Low FODMAP
From the Paleo diet, you can try a more specialized diet like low FODMAP or a low histamine diet. Again, you’ll follow this diet for two to four weeks and then reintroduce foods one at a time to identify any trigger foods.
These diets do tend to be more difficult for people to follow, but the trick is to remember that it’s not forever, and you’re doing this to feel better. In the beginning, stick to a few basic meals and be willing to repeat meals often until you get a handle on what foods you can eat. Then you can expand into more meals and more food options. It also helps to batch prepare meals and stock your freezer for times when you’re tempted to reach for something outside of the diet.
If you don’t notice any improvements in two to three weeks, you don’t have to force yourself to stay on the diet. At this point, it may be helpful to consult with a healthcare provider on next steps.
Probiotics for Gut Health and Allergies
Probiotics (beneficial bacteria) are another proven therapy for allergy relief via gut health and microbiome support.
Three systematic reviews found that probiotics are helpful for improving the incidence and symptoms of allergic rhinitis (seasonal allergies) [33, 34, 35].
Several randomized controlled trials also showed that probiotics are useful for seasonal allergies by improving quality of life [36, 37], allergy symptoms [38, 39, 40], and reducing the need for allergy medication . One review showed 11 out of 14 clinical trials where probiotics significantly improved seasonal allergy symptoms, and several studies also noted improved immune system balance .
We’re still learning about the role probiotics have in producing histamine and protecting the body from its effects.
But, there is in vitro (cell or petri dish) evidence that some common types of probiotics (Lactobacillus and Bifidobacterium) can reduce histamine [41, 42]. Additionally, one mouse model study found that a probiotic mixture was able to reduce allergy behaviors and decrease histamine signaling in mice . This evidence suggests the same could be true for people, but we need human clinical studies in order to find out.
Nonetheless, in the clinic, we’ve seen probiotics help many patients handle histamine more effectively and reduce symptoms of histamine intolerance.
Reducing Dairy Allergy/Lactose Intolerance
Probiotics may also help improve lactose intolerance symptoms.
One systematic review and meta-analysis found that probiotics improved cow’s milk allergy in children compared to placebo . A randomized controlled trial (RCT) found that probiotics combined with an elimination diet improved symptoms more than an elimination diet alone .
A review of nine RCTs investigated the effects of probiotics on lactose intolerance. A total of 304 subjects with lactose intolerance were included in the analysis. The results showed that probiotic use was associated with significant improvements in lactose intolerance symptoms and improved digestion (based on hydrogen breath test results) compared to control .
For lactose intolerance, the effects of probiotics may even last longer than enzyme supplements . Plus, probiotics are helping to make your microbiota stronger as a whole, to improve overall digestion of everything you eat. It’s a win-win.
Should I Take Probiotics While on an Elimination Diet?
You can take probiotics while on an elimination diet, such as Paleo or low FODMAP (and this is typically what we recommend). However, if you’re just starting to change your diet, you’ll want to hold off on probiotics for at least a couple of weeks to see how your body responds to the dietary changes on its own.
The idea is that if we do too many things at once, we won’t know what changes are making a difference, or not making a difference. But, for example, if you’ve been on a Paleo diet for three weeks and you’ve seen some significant improvements in your allergy symptoms, but you want to know if you could feel even better with probiotics, adding in a high-quality probiotic is a logical next step.
Find Allergy Relief By Supporting Gut Health
If you suffer from seasonal allergies, food intolerances, or even histamine intolerance, fortifying your gut health might be your ticket to enjoying the turn into spring and summer this year. Finding the right therapeutic diet and diversifying your gut microbiome with probiotics are two strategies that can go a long way toward reducing allergy symptoms.
The Ruscio Institute has developed a range of high-quality formulations, including all-in-one triple therapy probiotics, to help our patients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you.
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