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Understanding Hay Fever and Your IL33 Gene

Hay fever, also called allergic rhinitis, is an immune system overreaction to normally harmless airborne substances such as pollen, dust mites, and pet dander. Typical symptoms include sneezing, runny or blocked nose, itchy or watery eyes, and sinus pressure. The IL33 gene helps control part of this response by producing interleukin-33, a signaling protein that alerts the immune system to potential threats. Variations in IL33 can change how strongly your immune system reacts to allergens, which can influence how likely you are to develop hay fever or have more severe symptoms.

How IL33 Affects Allergy Risk

Interleukin-33 acts like an immune alarm. When released, it activates immune cells that promote a Th2 type immune response. Th2 responses drive the production of histamine and other inflammatory molecules that cause classic allergy symptoms. Certain genetic variants in IL33 can increase production or activity of IL-33, making the immune system more likely to overreact to everyday allergens. Your genotype at the rs1342326 location in the IL33 gene is one factor that can affect this pathway.

Two effect alleles (CC) — higher risk

Having the CC genotype at rs1342326 means you carry two copies of the effect allele. This variant is associated with an increased risk of developing hay fever and asthma. Your IL33-related signaling may be stronger or more easily triggered, which can promote Th2 immunity and inflammation. Practically this could mean more frequent or more severe sneezing, congestion, itchy eyes, and increased susceptibility to asthma symptoms when exposed to allergens.

Actionable steps for people with CC:

  • Work with your healthcare provider to develop a symptom management plan and discuss allergy testing if needed.
  • Prioritize allergen avoidance strategies at home and during peak pollen seasons.
  • Consider discussing anti-inflammatory or allergy medications with your clinician if symptoms interfere with daily life.
One effect allele (AC) — slight increase in risk

Having the AC genotype at rs1342326 means you carry one copy of the effect allele. This is associated with a modestly increased risk of hay fever and asthma compared to people without the effect allele. Your IL33 signaling may be somewhat more reactive, making you moderately more prone to allergy symptoms such as sneezing, runny nose, and itchy eyes. The size of this effect varies and depends on other genetic and environmental factors.

Actionable steps for people with AC:

  • Adopt basic allergy-prevention measures, especially during seasons when your symptoms flare.
  • Track triggers and symptoms to determine whether interventions like antihistamines or nasal sprays are useful.
  • Support overall immune balance through diet, sleep, and stress management.
No effect alleles (AA) — typical risk

Having the AA genotype at rs1342326 means you carry two copies of the non-effect allele. This suggests your IL33-related risk for hay fever and asthma is similar to the typical population risk for this specific genetic location. You do not carry the IL33 variant associated with increased susceptibility via this pathway. That does not mean you cannot get allergies. Many other genes and environmental factors influence allergic disease.

Actionable steps for people with AA:

  • Maintain general allergy prevention habits and monitor symptoms over time.
  • If symptoms develop or worsen, seek evaluation to identify triggers and appropriate treatments.
  • Consider lifestyle supports that lower overall inflammation and support immune regulation.

Dietary and Nutritional Strategies

Diet cannot change your genes but can influence inflammation and immune balance. Focus on whole foods that promote a healthy immune system and reduce chronic inflammation.

  • Eat a wide variety of colorful fruits and vegetables daily for antioxidants and bioactive compounds that help modulate immune responses.
  • Include omega-3 rich foods such as fatty fish, walnuts, flaxseeds, or algae-based sources to support anti-inflammatory pathways.
  • Prioritize fermented foods like yogurt, kefir, sauerkraut, and kimchi when tolerated to support a diverse gut microbiome.
  • Choose high-fiber whole grains, legumes, and vegetables to feed beneficial gut bacteria that influence immune health.
  • Limit highly processed foods and excessive sugar that can promote inflammation and dysregulated immunity.

Supplements That May Help

Supplements can complement diet when needed. Talk to your healthcare provider before starting any new supplements, especially if you take medications or have chronic conditions.

  • Vitamin C: A natural antioxidant that can support immune function and reduce severity of upper respiratory symptoms.
  • Quercetin: A plant flavonoid with natural antihistamine and anti-inflammatory properties. Often used by people with seasonal allergies.
  • Omega-3 fatty acids: Supplementation can reduce inflammatory signaling and may help with allergic inflammation.
  • Probiotics: Specific strains may support immune balance and have been associated with improvements in some allergic conditions.
  • Vitamin D: Adequate vitamin D supports immune regulation. Check levels with your provider before supplementing aggressively.

Lifestyle Steps to Reduce Symptoms

  • Allergen reduction: Use HEPA or high-efficiency filters, keep windows closed during high pollen times, wash bedding weekly in hot water, and use dust-mite covers if sensitive.
  • Personal habits: Shower and change clothes after outdoor exposure during pollen season to remove allergens from skin and hair.
  • Sleep and stress: Aim for consistent, restorative sleep and regular stress management practices like mindfulness or gentle exercise. Poor sleep and chronic stress can worsen immune reactivity.
  • Exercise: Regular moderate exercise supports immune health. Avoid intense outdoor workouts during peak pollen periods if you are sensitive.
  • Smoking and air quality: Avoid tobacco smoke and reduce exposure to indoor irritants that can amplify allergic inflammation.

When to See a Healthcare Provider

  • If symptoms are frequent, severe, or affecting quality of life, talk with your clinician about allergy testing and tailored treatment options.
  • Discuss pharmacologic options such as antihistamines, intranasal corticosteroids, or other prescription therapies if over-the-counter measures are insufficient.
  • Ask about immunotherapy if allergies are persistent and specific triggers have been identified. Immunotherapy can modify immune responses over time.
  • Consider checking nutrient levels such as vitamin D under medical supervision before starting high-dose supplementation.

Final Notes and Disclaimer

PlexusDx provides educational information about genetic predispositions and how they may relate to health and wellness. This content is for informational purposes only and does not constitute medical advice. Genetic results are one piece of the puzzle. Lifestyle, environment, and other genes also shape your risk. Always consult with your healthcare provider before making medical or major lifestyle changes based on genetic information. Your provider can help interpret these findings in the context of your overall health, symptoms, and medical history.