Allergic Rhinitis & COVID-19: Symptoms, Risks & Immunotherapy Impact

Allergic rhinitis, commonly known as hay fever, appears to influence the way individuals experience COVID-19, with recent research revealing a complex interplay between the allergy and the viral infection. A study conducted in China suggests that those with allergic rhinitis may be less prone to certain COVID-19 symptoms, like respiratory distress, but more susceptible to others, such as loss of smell and taste, and fever. The use of sublingual immunotherapy – a form of allergy treatment – appears to modify these effects, sometimes in unexpected ways.

Dual Effects of Allergic Rhinitis on COVID-19

The research, published in December 2025 in Scientific Reports, involved a retrospective analysis of over 1,368 individuals. Researchers examined the health records of 746 people with allergic rhinitis and 622 individuals without any known allergic conditions, all within one month of adjustments to China’s COVID-19 response measures. The study aimed to understand how pre-existing allergic rhinitis might impact the clinical presentation of COVID-19.

The findings revealed a somewhat paradoxical effect. Compared to those without allergies, individuals with allergic rhinitis were less likely to develop respiratory symptoms when infected with COVID-19. This suggests a potential protective association, though the underlying mechanisms remain unclear. However, the study also found that people with allergic rhinitis were more likely to experience alterations in their sense of smell and taste – known as olfactory and gustatory dysfunction – as well as fever. This indicates that allergic rhinitis may modulate the immune response to the virus in a complex manner, potentially shifting the balance of symptoms.

Sublingual Immunotherapy: A Complicated Picture

The study also investigated the impact of sublingual immunotherapy (SLIT) on COVID-19 outcomes in individuals with allergic rhinitis. SLIT involves administering small doses of allergens under the tongue to gradually desensitize the immune system. Of the 746 participants with allergic rhinitis, 122 were undergoing SLIT at the time of their COVID-19 infection, while 483 were not.

Interestingly, the results showed that those receiving SLIT had a higher risk of developing respiratory symptoms compared to those with allergic rhinitis who were not on immunotherapy. This finding is somewhat counterintuitive, given the potential protective effect of allergic rhinitis itself against respiratory symptoms. However, the SLIT group exhibited a lower risk of fever. The therapy did not appear to significantly influence the occurrence of smell and taste disturbances.

Researchers suggest that SLIT may alter specific inflammatory pathways involved in the body’s response to COVID-19. The therapy’s immunomodulatory effects could potentially influence how the virus manifests, leading to a different symptom profile. The increased risk of respiratory symptoms in the SLIT group warrants further investigation to understand the underlying mechanisms.

Clinical Implications and Considerations

These findings have important implications for clinicians managing patients with allergic rhinitis during periods of high COVID-19 transmission. The study highlights the need for careful evaluation of respiratory symptoms in allergic rhinitis patients, particularly when considering whether to initiate or continue SLIT. The altered risk of fever also warrants attention during clinical assessment and monitoring.

The research suggests that doctors should be particularly vigilant for respiratory symptoms in allergic rhinitis patients undergoing SLIT, while also being aware of the potentially reduced risk of fever in this group. These observations underscore the importance of individualized treatment approaches and careful consideration of the potential interplay between allergies, immunotherapy, and viral infections.

“These data suggest that immunomodulatory treatment may alter specific inflammatory pathways relevant to respiratory and systemic manifestations of COVID-19,” the study authors noted. Further research is needed to clarify the mechanisms driving these associations and to inform personalized treatment strategies for individuals with allergic rhinitis who are at risk of or infected with COVID-19.

The study’s findings emphasize the complex relationship between the immune system, allergies, and viral infections. As we continue to navigate the evolving landscape of respiratory viruses, a deeper understanding of these interactions will be crucial for optimizing patient care and public health strategies.

Reference

Zhang Y-Y et al. A retrospective cohort study on the association between allergic rhinitis, sublingual immunotherapy, and COVID-19 symptomatology. Scientific Reports. 2025;16:2159.