Your Diet Could Be Making Your Allergies Worse, New Study Suggests

Overdoing it on sodium could have some drawbacks during allergy season.

Reviewed by Dietitian Madeline Peck, RDN, CDN

Key Points

• This study suggests a connection between excess salt intake and worse hay fever symptoms.
• There are several possible reasons salt may worsen hay fever, including causing gut dysbiosis.
• Lower salt intake by cooking at home and limiting packaged, prepared and restaurant foods.

Allergic rhinitis (AR), AKA hay fever, is an allergic, inflammatory reaction to airborne substances, including pollen, mold, dust mites and pet dander. If you’re among the 10% to 40% of people worldwide with hay fever, chances are you’re frequently on the hunt for some relief from the sneezing, runny nose and congestion.

Some common remedies include allergy medication and avoiding the source of the allergy—which is often easier said than done. But there might be another way to reduce hay fever symptoms, starting with your salt shaker.

Since there is evidence that there is a connection between diet and allergic rhinitis, Canadian and Chinese researchers decided to examine how a high-salt diet might affect hay fever symptoms. They published their results in Science of Food. Let’s break down what they found.

How Was This Study Conducted?

This study was done in two primary parts. The first involved human participants, the second, mice.

For the human trial, 51 men and women between the ages of 18 and 65 were included. They had to exhibit symptoms of AR, including recurrent sneezing and an itchy, runny nose with pale, swollen nasal mucous membranes. They also had to test positive for IgE antibody levels exceeding 0.35 KUA/L. IgEs are antibodies produced by the immune system, causing inflammation as a reaction to allergic substances.

There were several exclusionary factors, as well. For example, participants needed to be free of mental illness, could not have used allergy medications within two weeks of the trial and could not have used pre- and postbiotic supplements, antibiotics or antacids within three months of the trial period.

Twenty-four-hour urinary sodium levels were measured at baseline. Based on these results, participants were split into high-salt diet and low-salt diet groups. Participants’ symptoms and IgE levels were then assessed.

For the animal study, mice were randomly divided into three groups. A control group and a low-salt group were fed a specific type of chow, and a high-salt group was fed the same chow but with added salt.

There were several stages to the animal study, including long-term and short-term interventions and reversing the high-salt diet to see if it improved AR symptoms. In addition, researchers tested the mice’s gut microbiomes, did bloodwork and tested their nasal symptoms.

What Did This Study Show?

At baseline, individuals with higher urine sodium levels exhibited more severe symptoms of AR compared to those with moderate and mild symptoms. After being divided into high- and low-salt diet groups, the high-salt group exhibited higher total IgE levels and more severe nasal symptoms, including nasal obstruction, compared to the low-salt diet group.

The high-salt diet mice also showed higher IgE levels and higher levels of other inflammatory factors that were tested, as well as significant exacerbation of AR symptoms. Researchers also observed a decrease in beneficial gut bacteria in the high-salt diet mice.

A limitation of this study is that the mouse trial might not translate to humans, though both showed similar results in this study. In human trials, there is always a risk of bias and confounding factors that may skew results. Researchers state that more research using larger human populations is necessary to draw firmer conclusions.

How Does This Apply to Real Life?

Previous human studies have linked high-sodium diets to allergic inflammatory responses, including inflammatory skin diseases like atopic dermatitis. In your body, metabolic processes take place via various pathways. This study and previous studies suggest that excess sodium appears to trigger certain inflammatory pathways.

Excess sodium may also negatively influence the immune system, and if your immune system isn’t working properly, you’re more likely to experience inflammatory responses—which may make conditions like hay fever worse.

Also linked to your immune system is your gut microbiome. This study and others suggest that high-salt intake may cause dysbiosis, knocking off the ratio of good-to-bad gut bacteria. There is also evidence in animal studies that excessive salt consumption may cause leaky gut syndrome, a condition where the cells lining your intestine aren’t fit tightly together, allowing substances to leak from the intestines into the body, causing inflammation.

While sodium is a necessary nutrient, most Americans consume too much of it. The American Heart Association recommends eating no more than 2,300 mg per day, with an optimal target of 1,500 mg, but Americans consume an average of 3300 mg of sodium per day. And since most of our sodium comes from packaged, prepared and restaurant foods, it’s important to try to cook at home as much as possible. Reading labels will also help you determine the amount of sodium in packaged foods.

If you’re ready to start cooking more at home, we have a slew of low-sodium and anti-inflammatory meal plans. Our weeklong Anti-Inflammatory Meal Plan for Leaky Gut is a great place to start. Or consider following the DASH diet, which is a low-sodium diet designed to help lower blood pressure.We’ve got a great beginner’s meal plan for that, too.

Another area to consider with AR is histamine, a substance released in your body as a result of being exposed to allergens. Some foods contain histamines, so when added to environmental allergies, they can increase your body’s inflammatory response even more. This includes fermented foods, certain fruits and vegetables, dairy, processed meats, alcohol and vinegars.

There’s also a condition called food-pollen allergy syndrome. Certain foods have been shown to be cross-reactive with pollen allergies, making symptoms worse. For example, if you’re allergic to grass, you might want to avoid melons, peaches, oranges and tomatoes during grass-allergy season. If you’re concerned about the severity of your allergies, consider talking to a healthcare professional to get more personalized advice and treatment.

Our Expert Take

This study suggests that there may be a connection between high salt intake and worsening allergic rhinitis symptoms. While sodium is a necessary nutrient, our bodies require only a small amount of it per day—less than 2300 mg. A high-salt diet may worsen allergic rhinitis through several mechanisms, including creating gut dysbiosis and triggering inflammatory pathways. You can lower your sodium intake by cooking at home and limiting highly processed, packaged and restaurant foods. If you want to explore whether you have histamine sensitivities or food-pollen allergy syndrome, work with an allergy medical professional and a registered dietitian.