Changes To Your Diet Can Affect Your Allergies - Here's How

Allergic reactions are a very common occurrence in the United States, affecting more than 50 million people annually (per Cleveland Clinic). People with airborne (inhalant) allergies often suffer from stuffy nose, runny nose, sneezing, and itchy/watery eyes. Among seasonal allergies, tree pollens trigger allergies in the spring, while weed pollens appear in the fall. Perennial (year-round) allergies include dust mites, cockroaches, molds, and pet allergens (e.g., fur, dander). Hives or itching shortly after eating may be a sign of an allergic reaction to a food. Severe reactions (anaphylaxis), marked by swelling of the mouth, throat, tongue, or face, can also occur in response to eating certain foods. Food allergies common in both children and adults include milk, egg, wheat, soy, peanut, and tree nuts. 

In some people, certain medications and herbal supplements can also elicit an allergic reaction. For example, some antibiotics may cause rashes, itchiness, swelling, or breathing problems. Another source of allergic reactions (usually skin rash) is latex, found in rubber products such as balloons, rubber gloves, and condoms. Venom from stinging insects (bees, wasps, and hornets) can also cause allergic reactions. Symptoms can include shortness of breath, swelling in the throat, wheezing, rapid heartbeat, dizziness, and low blood pressure. 

The increasing prevalence of allergies may be partly due to the "hygiene hypothesis," which states that children with limited exposure to germs develop an overreactive immune system that leads to allergies and allergic diseases later in life (via a 2021 review in Foods). 

Apples, berries, and onions are among the richest food sources of the potent flavonoid compound quercetin (via Life Extension). Other excellent sources include dark-colored grapes, kale, capers, buckwheat, and green tea. Quercetin's antioxidant and anti-inflammatory properties contribute to many health benefits, including supporting healthy immune function, blood pressure, and blood sugar, as well as the elimination of old, inflammatory senescent cells that accumulate with advancing age. 

According to a 2016 review in Molecules, quercetin also has anti-allergy properties. Quercetin suppresses the production of and secretion of histamine from mast cells and basophils (another type of immune cell) sensitized by allergens. Histamine and other chemicals are responsible for common allergy symptoms such as itching, sneezing, and watery eyes. Quercetin also inhibits the release of inflammatory chemicals known as cytokines from mast cells, accounting for its therapeutic effect against allergic inflammatory diseases such as asthma. Moreover, animal studies have shown that over a quarter of absorbed quercetin concentrates in lung tissue. 

As an anti-allergy agent, quercetin functions specifically as a mast cell stabilizer, a drug or natural compound that stabilizes the membranes of mast cells, preventing their activation and blocking the releases of histamine and other chemicals. In fact, quercetin is structurally similar to cromolyn, a medication used to prevent allergic reactions. Impressively, quercetin is more effective than cromolyn at suppressing the release of inflammatory cytokines from mast cells. With regard to food allergy, quercetin has been shown in animal models to significantly inhibit the IgE allergic response against peanut proteins. 

According to a 2019 study in the World Allergy Organization Journal, capsaicin is the main bioactive ingredient in cayenne pepper that is responsible for its spicy taste, as well as various health benefits. Antioxidant and anti-inflammatory properties associated with capsaicin may contribute to its potential benefits in the management of food allergy. In a mouse model of food allergy, supplementation with capsaicin was shown to decrease allergic inflammation and oxidative stress (free radical damage). This resulted in lower levels of interleukin 33 (IL-33), a proinflammatory cytokine that plays an important role in the development of allergic diseases. The study authors suggest that continuous consumption of capsaicin over a longer period may mitigate food allergy. 

Another popular spice, ginger, can improve symptoms related to seasonal allergies (via a 2016 study in The Journal of Nutritional Biochemistry). Ginger has been used for centuries in Chinese and Indian medicine to treat nausea, asthma, and other disorders. Ginger also has antiallergy effects owing to its major bioactive component known as 6-gingerol. In mice with allergic rhinitis (hay fever), administration of ginger powder and 6-gingerol alleviated allergy symptoms such as sneezing and nasal rubbing. Specifically, 6-gingerol was demonstrated to inhibit the production of inflammatory cytokines, thus preventing the activation of mast cells that would otherwise release histamines that trigger symptoms of allergic rhinitis. 

For centuries, honey has been used in folk medicine to treat various ailments such as burns, wounds, cough, asthma, gastrointestinal illnesses, and cardiovascular disorders (via a 2020 mini review of studies published in Frontiers in Pharmacology). Today, research evidence supports some of the therapeutic effects of honey, including anti-inflammatory, antioxidant, antimicrobial, antidiabetic, and anticancer activity. The health benefits of honey may be attributed to its high number of flavonoids, polyphenols, and other phytochemical (plant) compounds.

Evidence from studies, though few, indicate that honey also has exceptional anti-allergic effects. For example, clinical studies have shown that the consumption of honey substantially improves allergic conditions such as allergic dermatitis and allergic rhinitis. One mechanism for the anti-allergic action of honey is the inhibition of histamine release from mast cells. Honey may also prevent allergic reactions by lowering levels of IgE, an antibody that plays a critical role in allergies and allergic disorders. Manuka and Tualang honeys are the most effective varieties for treating allergic diseases, likely because of the extensive number of bioactive compounds they contain, e.g., gallic acid, kaempferol, and caffeic acid.

Olive oil is the predominant source of fat in the Mediterranean diet, which is linked to lower rates of cardiovascular disease, cancer, diabetes, and other chronic conditions (via a 2019 review of studies published in the journal Nutrients). The Mediterranean diet is also protective against allergies and allergic diseases, particularly asthma. Some studies indicate that the olive oil in the diet is a major source of bioactive compounds that exert anti-inflammatory and antioxidant effects to reduce asthmatic symptoms. For example, in a study of Italian adults, increasing olive oil consumption by 2 1/4 teaspoons per day was associated with a 20% lower risk of asthma. 

One of the most potent anti-inflammatory compounds in olive oil is known as hydroxytyrosol. In a cell culture study, human immune cells were stimulated by both a pollen allergen and hydroxytyrosol. The resulting response of the immune cells was a significantly increased secretion of interleukin 10 (IL-10), an anti-inflammatory cytokine. In effect, hydroxytyrosol derived from olive oil was shown to reinforce a healthy immune response against an airborne allergen. Polyphenols from extra virgin olive oil have also been shown to mitigate skin inflammation. 

As reported thus far, a variety of foods can have a favorable impact on allergies. But there are also foods that may worsen or increase the risk of allergies, and it's the same foods that harm us in other ways as well. 

In a 2022 study published in the European Journal of Allergy and Clinical Immunology, a high intake of dietary sugars and starches was shown to correlate with a higher prevalence of asthma in humans. In mice, a high-carbohydrate diet worsened allergic airway inflammation compared to a high-fat diet. The increased lung inflammation in the mice on the high-carb diet was associated with increased oxidative stress (free radical damage) in the lungs together with decreased body-wide antioxidant defenses to counter oxidative stress. A preferential use of glucose rather than fat for energy was also reported. Interventional trials in humans are recommended to confirm these findings. 

Sugar may even play a role in allergic diseases before you are born. According to a 2021 systematic review and meta-analysis published in the journal Medicine (Baltimore), a high intake of sugar during pregnancy puts the developing fetus at risk for the development of allergies. This may be linked to the ability of sugar to activate systemic inflammation. Alternatively, it was suggested that allergies and allergic diseases in the offspring may develop indirectly as a consequence of overweight and obesity.