As pollen soars and we move from tree pollen season to grass pollen season in the UK, it seems an opportune time to explore the topic of allergic rhinitis – or ‘hay fever’ (Met Office, 2025), which is the most common allergy presentation in the world, affecting 400 million people globally (Waage et al, 2018). Interestingly, the term ‘hay fever’ came into existence because it was originally believed that the symptoms of allergic rhinitis were caused by the smell of hay (Dinning, 2018; London Allergy and Immunology Centre, 2018).
However, while hay season and pollen season coincide, it is the pollen, whether from trees, grass, flowers or weeds, that causes seasonal hay fever, as was officially discovered in 1859 by Manchester physician, Charles H Blackley (London Allergy and Immunology Centre, 2018). Oddly, however, even once the true cause was established, the misnomer ‘hay fever’ has stood the test of time. Hay fever has been written about for the last 200 years, although at the time, allergies were not understood and pioneering research carried out by English physician, John Bostock, was perplexing to people of the day (London Allergy and Immunology Centre, 2018).
It must be noted that not all allergic rhinitis is seasonal; and indoor allergens, from pet dander and cockroach droppings to dust mites and mould spores, can cause allergic rhinitis throughout the year (Allergy UK, 2025).
What is hay fever?
Hay fever is a common allergic reaction that takes place when an individual's immune system overreacts to allergens that are present in the air (Allergy UK, 2025). It affects somewhere between 10 and 16 million individuals in the UK, or close to a quarter of the population (London Allergy and Immunology Centre, 2018; McDougall, 2024; Ahmed and Whitaker, 2025). One study carried out by Allergy UK places this figure at double this estimate (Holroyd, 2021).
However, on closer scrutiny, this study took place over the COVID-19 pandemic, which marked the beginning of confusion between symptoms of hay fever and COVID-19 (BBC, 2020; Smith, 2025). In fact, even the study itself found that 56% of people were worried that their hay fever symptoms may be mistaken for COVID-19 (Allergy UK, 2025). Furthermore, the study was in partnership with Kleenex (Holroyd, 2021) – a company that arguably stands to benefit from such findings. Also, because factors such as stress and infections can trigger an overactive immune response (McDougall, 2024), it is not too far-fetched to theorise that hay fever symptoms may have risen during the pandemic.
Symptoms of hay fever include the following and can vary from individual to individual (Akhouri and Rhinitis, 2023; NHS, 2024; Roberts, 2025):
Symptoms of hay fever are at their worst between late March and September when pollen counts peak and when it is warm, humid and windy enough for it to be blown about (NHS, 2024). However, as mentioned, there are also indoor triggers and hay fever can be chronic (or perennial), rather than intermittent/seasonal particularly in adults (Akhouri and Rhinitis, 2023).
What causes hay fever?
Hay fever is caused by a histamine response from the immune system when it is overwhelmed by triggers in the air (e.g. pollen, dust mites, pet dander) (Allergy UK, 2025). When a person with hay fever is exposed to such allergens, their immune system releases histamines and other chemicals, which causes symptoms such as those mentioned in the previous section. Seasonal hay fever, in particular, is common and determined by pollen seasons.
‘While antibiotics are important in the treatment of serious bacterial infections, and their use should be based on careful medical evaluation … early antibiotic use may disrupt the development of the immune system’
It is further affected by the weather, an individual's geographical location, and even climate change. Interestingly, hay fever (both seasonal and perennial) also has a genetic component and has been shown to be affected by early exposure to antibiotics.
Weather, geography and climate change
In the UK, the hay fever season starts with tree pollen from late March to the middle of May, affecting one in four people (Met Office, 2025). This is followed by the grass season from approximately mid-May to July, including two peak seasons (that are dependent on geographical location) (Met Office, 2025), although fungal spores can be released until September or October (NHS Waltham Forest Clinical Commissioning Group (CCG), 2017; Roberts, 2025).
The peak grass pollen season across England and Wales usually starts in the first 2 weeks of June. The second lower peak season is usually around the first 2 weeks of July (Met Office, 2025). Peaks can be masked by the weather; for example, how wet or dry it is, how warm or cold it is, and even wind and sunlight play a role (Met Office, 2025).
Weed pollen can be released at any time, but it is typically present from around the end of June until September (Met Office, 2025). The north of the UK tends to experience a later start to the pollen season, and a shorter season overall (Met Office, 2025). Interestingly, while pollen is typically higher in the countryside than it is in cities, towns and cities have seen a much larger extension of their pollen season as a result of rising temperatures caused by climate changes (Bawden, 2025). A total of 131 UK towns and cities registered an increase of at least 21 days since 1994, while eight cities have had their hay season extended by an average of 29 days a year – and these numbers are expected to continue to increase (Bawden, 2025).
Genetic component
Genetics also play a role in an individual's predisposition to hay fever. In fact, a large international study, published in Nature Genetics, examining the genetic role in hay fever identified 41 associated genes, 20 of which were only linked with allergic rhinitis for the first time by this study (Waage et al, 2018). Waage et al (2018) carried out a meta-analysis of 59 762 cases of allergic rhinits and 152 358 controls of European descent.
A replication phase followed this with 60 720 cases and 618 527 controls. A genome-wide association study (GWAS) was then carried out to identify genetic patterns to being sensitive to allergens such as pollen or dust mites and the authors discovered shared genetic mechanisms across traits related to hay fever (Waage et al, 2018).
The study revealed that most of the 20 newly identified gene factors are involved in immune system function and found an overlap between risk genes for hay fever and autoimmune diseases like type 1 diabetes and rheumatoid arthritis (The Pharmaceutical Journal, 2018).
While genetics are only factor among many related to the development of hay fever, Waage et al's (2018) findings could help to inform targeted treatments and preventive strategies.
Early antibiotic exposure
An individual's gut microbiota are also believed to play an important role in the development of their immune system. According to Fariba Ahmadizar from Utrecht University in the Netherlands, who was the lead author of a systematic review carried out in 2016, early antibiotic exposure can lead to reduced gut microbial diversity, leading to imbalanced immune responses and increased risk of allergies (Oswald, 2016).
The review examined the link between early antibiotic use and the development of hay fever later in life. Researchers analysed data from 22 observational studies involving 256 609 individuals for hay fever. The findings revealed that the odds of developing hay fever were increased by 56% in those individuals who received antibiotics in their first 2 years of life, with this risk being even higher for those who received multiple courses of antibiotics (Oswald, 2016). They also investigated eczema risk, which is beyond the focus of the current article, but which was also increased by up to 41%.
While antibiotics are important in the treatment of serious bacterial infections, and their use should be based on careful medical evaluation, the findings of this study suggest that early antibiotic use may disrupt the development of the immune system, potentially increasing the risk of allergic conditions such as hay fever.
How is hay fever treated?
In the past
Historically, methods to try to treat hay fever were decidedly questionable. Bostock, the first person to accurately describe the condition, suffered from it himself and tried everything from the use of opium, purging, ‘topical bleeding’ and even courses of mercury (Dinning, 2018). An American article from more than 75 years later reveals that contemporary doctors recommended visiting the seaside, taking a trip on a yacht, burying oneself in a ‘densely populated town’ or the use of tobacco, ‘the smoke being retained in the mouth as long as possible, and ejected through the nose’ (Dinning, 2018).
Current approaches
Rather unsurprisingly, none of these methods worked, but Bostock did note that his symptoms eased when he confined himself to his home for 6 weeks (Dinning, 2018). Avoidance of one's allergens is essential for the management of allergic rhinitis and, of course, prevent symptoms. For those whose condition is chronic, some changes can be made, such as isolating a pet to one room, use of allergenimpermeable bedding covers, washing sheets in hot water, and use of a vacuum cleaner with highefficiency particulate air (HEPA) filters (Akhouri and House, 2023).
Pharmacological treatments to control symptoms include antihistamines, intranasal steroids, leukotriene receptor antagonists (LTRAs), and immunotherapy (Akhouri and House, 2023). Oral antihistamines, intranasal corticosteroids and antihistamine eye drops are first-line treatments for hay fever and are available over the counter (NHS Walham Forest CCG, 2017; The Pharmaceutical Journal, 2020). Common treatments are available as oral tablets, sprays or eye drops.
According to Akhouri and House (2023), intranasal corticosteroids (e.g. fluticasone, budesonide) are the most effective first-line treatment for allergic rhinitis, and are superior to antihistamines for reducing inflammation. They note that correct spray technique and regular use are essential. Second-generation antihistamines such as cetirizine and fexofenadine are less drowsy than first-generation options. Fexofenadine 120 mg tablets were moved to the General Sales list in 2020 after a 20-year established safety profile as a prescription only medicine (POM), though the 180 mg tablets for symptoms associated with chronic idiopathic urticaria in adults and adolescents aged 12 years or older, and 30 mg tablets for symptoms associated with seasonal hay fever in children aged 6–11 years are still available are POMs.
Akhouri and House (2023) suggest that intranasal antihistamines such as azelastine act quickly and can be combined with steroids, and that montelukast may help in severe cases but is less effective overall. Immunotherapy is considered when medications fail (Akhouri and House, 2023). Decongestants offer short-term relief but risk rebound congestion and should not be used for more than 1 week (Akhouri and House, 2023). Sodium cromoglycate is effective for relieving sneezing, rhinorrhea and nasal pruritic, and nasal saline is an option in conjunction with other treatment modalities (Akhouri and House, 2023). They highlight that budesonide is safe during pregnancy, and omalizumab is effective but costly. Surgery is reserved for resistant structural issues (Akhouri and House, 2023).
Towards the future
In terms of complementary and alternative medicine, there are also homeopathic remedies available (Leadbetter, 2023) and, while literature is limited, studies demonstrate some small benefits of homeopathic nasal sprays on nose and eye symptoms of hay fever (Banerjee et al, 2017), while individualised homeopathic treatment has ben associated with significant alleviation of hay fever symptoms (Pandey, 2016).
Innovative approaches are also under way, with genetically modified rice designed to alleviate hay fever in development in Japan since 2000 and, while this faced regulatory hurdles, recent approval of a new clinical study means that this novel approach is now moving towards clinical application (Kobayashi, 2025).