Allergies After COVID: Key Insights and Precautions

Some people have reported new or worsened allergies after recovering from COVID-19, raising questions about how the virus affects immune responses. Emerging evidence suggests post-COVID immune shifts may increase sensitivity to allergens, impacting respiratory health, skin reactions, and food tolerances.

Understanding these changes can help individuals recognize symptoms early and take precautions.

Immune Adjustments And Allergy Onset

SARS-CoV-2 infections can cause lasting immune regulation changes that may trigger or worsen allergies. Research indicates post-viral immune dysregulation can heighten reactivity to allergens by disrupting the balance between tolerance and hypersensitivity. A study in The Journal of Allergy and Clinical Immunology (2023) found that post-COVID individuals exhibited increased type 2 helper T cells (Th2), which drive allergic responses. This shift may lead to new allergies or intensify existing ones.

Another factor is the dysregulation of regulatory T cells (Tregs), which normally suppress excessive inflammation. Research in Nature Immunology (2024) found reduced Treg function in post-COVID immune profiles, leading to increased mast cell and eosinophil activity—both central to allergic reactions. This imbalance may explain heightened sensitivity to allergens like pollen, dust mites, or pet dander.

Changes in cytokine signaling may also play a role. Elevated levels of interleukin-4 (IL-4), interleukin-5 (IL-5), and interleukin-13 (IL-13), all linked to IgE-mediated allergic responses, have been observed in post-COVID patients. A Lancet Respiratory Medicine (2024) meta-analysis found individuals with prolonged inflammation had a higher likelihood of developing allergic symptoms, suggesting persistent immune activation fosters allergic susceptibility.

Upper And Lower Respiratory Symptoms

Many recovering from COVID-19 report lingering or new respiratory issues resembling allergic reactions. Persistent nasal congestion, sneezing, and increased mucus production overlap with allergic rhinitis. A JAMA Otolaryngology–Head & Neck Surgery (2023) study found nearly 30% of post-COVID individuals experienced prolonged nasal inflammation, even without prior allergies, suggesting lasting effects on nasal mucosa reactivity.

Lower airway sensitivity has also been reported, with symptoms like coughing, wheezing, and shortness of breath. A European Respiratory Journal (2024) review found post-COVID individuals without asthma exhibited airway hyperresponsiveness similar to allergic asthma. Structural changes in the bronchial epithelium, including increased mucus gland hypertrophy and epithelial barrier dysfunction, may amplify sensitivity to airborne irritants.

Concerns about long-term airway remodeling persist, as chronic inflammation can cause structural changes that increase susceptibility to obstruction and irritation. A American Journal of Respiratory and Critical Care Medicine (2024) study following post-COVID patients for 12 months found those with persistent respiratory symptoms had elevated eosinophil and neutrophil levels, markers of allergic and non-allergic inflammation. Even individuals without prior respiratory allergies may develop heightened bronchial reactivity post-infection, increasing sensitivity to environmental triggers like smoke, pollution, and seasonal allergens.

Skin And Mucosal Changes

Post-COVID individuals have reported unexpected skin and mucosal changes, including dryness, heightened sensitivity, and inflammatory reactions. Dermatologists have noted increased cases of new or worsening eczema, hives, or rashes, even in those without prior skin conditions.

One potential cause is disruption of the skin’s lipid barrier, which retains moisture and protects against irritants. Many post-COVID individuals develop xerosis (abnormal skin dryness), leading to itching and increased sensitivity to fragrances, detergents, and fabrics. This is particularly common in those who experienced prolonged fevers or systemic inflammation, as excessive sweating and dehydration impair skin hydration.

Mucosal tissues, particularly in the mouth and eyes, have also shown persistent irritation. Patients report dry mouth (xerostomia) and dry eye syndrome, often resembling allergic conjunctivitis without a clear allergen trigger. Ophthalmologists suspect COVID-19 may disrupt tear film composition, reducing the eye’s ability to flush out irritants effectively.

Cross-Sensitization Patterns

Some individuals recovering from COVID-19 have developed allergic reactions to substances they previously tolerated, prompting investigations into cross-sensitization. This occurs when exposure to one allergen increases sensitivity to structurally similar allergens, as seen in pollen-food syndrome and latex-fruit syndrome. Scientists are exploring whether COVID-19 alters sensitization pathways, leading to new allergic responses.

One area of interest is increased reactivity to inhalant allergens that share molecular similarities with certain foods. Individuals with pollen allergies sometimes experience oral itching or swelling when consuming related fruits or vegetables. Some allergists report cases where post-COVID patients develop food sensitivities, particularly those with pre-existing environmental allergies. While mechanisms remain under investigation, early findings suggest post-viral changes in epithelial barrier integrity may enhance allergen absorption, increasing cross-reactivity risk.

Food Sensitivity Manifestations

Some post-COVID individuals report unexpected food-related reactions, including gastrointestinal discomfort, oral irritation, and heightened sensitivity to certain ingredients. While some cases stem from lingering inflammation, others suggest changes in how the body processes food proteins.

One commonly reported issue is increased sensitivity to histamine-rich foods like aged cheeses, fermented products, and cured meats. Researchers are examining whether post-COVID alterations in enzymatic activity—specifically in diamine oxidase (DAO), which breaks down histamine—contribute to these reactions. A Gastroenterology (2024) study found some post-COVID individuals had decreased DAO activity, leading to headaches, flushing, and digestive disturbances after consuming histamine-laden foods. Rather than true allergies, these cases may reflect temporary enzyme deficiencies affecting histamine metabolism.

Another concern is increased intestinal permeability, or “leaky gut,” where damage to the gut lining allows partially digested food particles to enter the bloodstream, triggering inflammatory responses. Some clinicians report more patients experiencing bloating, cramping, and irregular bowel movements after consuming gluten or dairy, even without prior sensitivities. Research is ongoing, but restoring gut barrier integrity through diet modifications and probiotics is being explored as a potential intervention for post-COVID digestive issues.