Spring and allergies: how to prepare for pollen season

Editorial Note

This article was previously published and has been updated according to scientific and informative criteria to reflect more recent and verifiable evidence. The text is for informational purposes only and does not replace the advice of a treating physician. In case of severe symptoms or clinical doubts, consult a healthcare professional.

IN BRIEF

• Seasonal allergic rhinitis is a common disorder, mediated by IgE-type immune responses and effector cells such as mast cells and basophils.
• The duration and intensity of pollen seasons have increased in many areas, with contributions attributable to climate change and increased CO2 concentrations.
• Options with the strongest evidence of efficacy include nasal corticosteroids and, for selected cases, allergen immunotherapy; dietary measures and the role of the microbiota are promising but not definitive.
• Practical recommendations are based on risk/benefit ratio and individual preferences; integrated management is often the most useful.

Abstract: what does science say?

Seasonal allergic rhinitis is an inflammation of the nasal mucous membranes triggered by exposure to airborne allergens (especially pollen). Clinical and experimental evidence shows that the reaction is mediated by IgE antibodies and the release of inflammatory mediators (histamine, leukotrienes) by mast cells and basophils. In recent decades, the prevalence of allergic diseases in pediatric age has increased in many regions, and the pollen season has become longer and, in several areas, more intense. The most established therapies for symptom relief include nasal corticosteroids and antihistamines; to modify the natural history of the disease, allergen immunotherapy remains the option with the most robust evidence. Observational associations exist between lifestyle, diet, gut microbiota composition, and allergic risk; however, these results do not automatically imply causality and require further experimental confirmation and clinical trials. The recommended approach is integrated, personalized, and evidence-based, with attention to the limitations of available studies.

Why it happens: relevant mechanisms

Immunological mechanisms

The typical manifestations of allergic rhinitis are the result of an immediate-type immune reaction mediated by immunoglobulin E (IgE). After exposure to an allergen (e.g., pollen), the antigen can bind to preformed IgE present on the surfaces of mast cells and basophils; the cross-linking of these receptors causes rapid degranulation and the release of mediators such as histamine, prostaglandins, and leukotrienes, which cause itching, sneezing, rhinorrhea, and congestion. In later stages, cells and cytokines are activated, amplifying and prolonging local inflammation, with a possible impact on sleep and daily activities. This picture is well documented in immunological literature and forms the biological basis of most modern symptomatic therapies [1].

Role of the microbiota

The microbiota, particularly the gut microbiota, is involved in the development and regulation of the immune system in the early stages of life. Observational data and experimental studies suggest that alterations in microbial composition (dysbiosis) can influence the predisposition to atopic diseases, including allergic rhinitis and food allergies. Proposed mechanisms include the modulation of Th2 responses, the production of immunomodulatory metabolites (such as short-chain fatty acids), and the effect on the maturation of regulatory cells. Although the role of the microbiota is plausible and supported by preclinical models and human studies, the ability to reliably intervene on the bacterial population to prevent or treat allergies requires further experimental and clinical evidence [4].

Evolution and trend: how society and climate impact it

In recent decades, an increase in the prevalence of allergic diseases has been observed in many regions, with particularly evident effects among children. This increase cannot be explained solely by genetic changes and has focused attention on environmental and lifestyle factors, including the "old friends" hypothesis and the possible loss of beneficial microbial exposures in immune development. At the same time, surveillance studies and environmental analyses show that the pollen season has, in several areas of North America and beyond, started earlier and lasted longer than in the past; in part, this phenomenon is attributable to global warming and rising average temperatures, which extend the plant growth period and can increase pollen production [3]. These trends have public health relevance: prolonged and, at times, more intense exposure increases the contact time with airborne allergens and can worsen symptoms in sensitized individuals. However, it is important to remember that the relationship between environmental change, increased prevalence of allergies, and clinical severity is complex and modulated by many social, housing, and biological variables [2][3].

What science says about the most effective measures

Available pharmacological treatments

For symptom relief, nasal corticosteroids are among the most effective treatments, especially for nasal congestion; antihistamines (oral and nasal) are useful for itching, sneezing, and rhinorrhea. Recent systematic reviews and meta-analyses confirm the general efficacy of these drugs and show differences in efficacy and certainty of evidence depending on the active ingredient and formulation. The choice of medication should consider symptom intensity, impact on quality of life, and tolerability [5].

Allergen immunotherapy (AIT)

Specific immunotherapy (subcutaneous or sublingual) is the only therapeutic option that, in controlled studies, has shown the ability to modify the course of the disease by reducing symptoms and medication use over time and, in some cases, progression to asthma. Systematic reviews and meta-analysis overviews document clinical benefits for selected patients when AIT is conducted with appropriate products and protocols and for an adequate duration (typically years). The decision for AIT requires specialist evaluation and an individual risk/benefit assessment [6].

Diet and lifestyle

Observational studies suggest associations between dietary patterns rich in fruits and vegetables (e.g., adherence to a Mediterranean diet) and a lower prevalence of allergic respiratory symptoms in some populations; genetic-epidemiological studies also indicate a possible causal role of specific lipid components (PUFA) on some allergic phenotypes. However, direct experimental evidence demonstrating the efficacy of dietary interventions in consistently preventing or treating allergic rhinitis is limited and often heterogeneous. Therefore, while it is plausible that a diet rich in anti-inflammatory nutrients and good sleep hygiene and physical activity contribute to general well-being, specific recommendations for the prevention or treatment of allergy remain cautious [7][8].

What it means in practice

For a person suffering from seasonal rhinitis, the practical application of scientific evidence translates into several operational principles: first, a correct diagnosis (clinical evaluation and, if indicated, allergy tests) allows distinguishing allergic rhinitis from other causes of nasal congestion. Well-documented symptomatic therapies (nasal corticosteroids, antihistamines) offer relief and improve sleep quality and daily activities; the prescription must be personalized and monitored. For cases with persistent symptoms or a strong impact on daily life, evaluation for allergen immunotherapy may be appropriate to modify the course of the disease. Practical measures to reduce pollen exposure (consult local bulletins, limit outdoor activities during pollen peaks, wear glasses and change clothes after outdoor activities) can reduce the exposure load but do not replace medical treatments. Finally, promoting healthy lifestyles and, when indicated, discussing with the doctor the possible usefulness of complementary interventions (e.g., specialist allergological support, educational programs) is a prudent and evidence-based approach.

Key points to remember

• Seasonal allergic rhinitis is mediated by IgE and mast cell/basophil degranulation; the main symptoms are sneezing, rhinorrhea, itching, and nasal congestion [1].
• The pollen season has become longer and in some areas more intense, with contributions attributable to climate change; this can increase exposure and symptoms in sensitized individuals [3].
• Nasal corticosteroids represent the reference symptomatic therapy; antihistamines and intranasal combinations are useful for specific symptoms [5].
• Allergen immunotherapy is the option with evidence of modifying the natural history in selected patients and should be evaluated by specialists [6].
• The microbiota and diet are active research areas: relevant associations exist, but the translation into preventive or therapeutic recommendations remains cautious [4][7][8].

Limitations of evidence

Available knowledge comes from different types of studies: observational (surveys, cohorts), experimental (animal models), randomized clinical trials, and systematic reviews. It is essential to distinguish observational results from causal evidence: associations (e.g., between diet or microbiota and allergic risk) do not automatically imply that intervening on those variables will produce the same effect. Methodological variability (outcome definitions, exposure measures, geographical and seasonal heterogeneity) limits generalizability. Many trials have modest sizes, short durations, or adherence problems, and endpoints differ between studies. Even in environmental analyses, the relationship between increased pollen and individual clinical impact is mediated by sensitivity, comorbidities, and access to care. For these reasons, recommendations must consider the certainty of the evidence and the individual clinical situation [2][3][4].

Editorial conclusion

The spring season brings with it the return of pollen and, for many people, a worsening of respiratory symptoms. Science has clarified the basic immunological mechanisms and has produced robust evidence for some symptom treatment options and for immunotherapy as a long-term strategy in selected patients. At the same time, environmental and lifestyle factors — including climate change and gut microbiota composition — can influence the frequency and severity of cases in the population. In practice, effective management requires accurate diagnosis, evidence-based treatment, patient education, and attention to the limitations of available research. For individual decisions, consulting a healthcare professional remains the most prudent choice.

Editorial Note (bottom of article)

Article updated according to scientific and journalistic review criteria. The information reported here is for informational purposes only and does not replace individual clinical evaluation. For specific medical questions, consult a medical specialist.

SCIENTIFIC RESEARCH

1. IgE and mast cells in allergic disease. Nat Med. 2012. https://doi.org/10.1038/nm.2755 [support for immunological mechanisms].
2. New progress in pediatric allergic rhinitis. Front Immunol. 2024. https://doi.org/10.3389/fimmu.2024.1452410 [pediatric evidence and epidemiology].
3. Anthropogenic climate change is worsening North American pollen seasons. Proc Natl Acad Sci U S A. 2021. https://doi.org/10.1073/pnas.2013284118 [climatic impact on pollen].
4. Food allergy and the gut. Nat Rev Gastroenterol Hepatol. 2017. https://doi.org/10.1038/nrgastro.2016.187 [role of the microbiota in allergies].
5. Intranasal antihistamines and corticosteroids in allergic rhinitis: a systematic review and meta-analysis. J Allergy Clin Immunol. 2024. https://doi.org/10.1016/j.jaci.2024.04.016 [evidence on intranasal treatments].
6. Allergen immunotherapy for allergic rhinoconjunctivitis: a systematic overview of systematic reviews. Clin Transl Allergy. 2017. https://doi.org/10.1186/s13601-017-0159-6 [summary on immunotherapy].
7. The causal association of polyunsaturated fatty acids with allergic disease: a two-sample Mendelian randomization study. Front Nutr. 2022. https://doi.org/10.3389/fnut.2022.962787 [genetic-epidemiological evidence on PUFA].
8. Adherence to an Anti-Inflammatory Diet and Atopic Diseases’ Prevalence in Adolescence: Global Asthma Network data. Nutrients. 2022. https://doi.org/10.3390/nu14081618 [associations between diet and atopic diseases].

Notes: the research listed above has been verified for DOI, title, and content scope. The numerical citations in the text correspond to their order of appearance and can be consulted via the DOI links for further details.