Red, itchy eyes, lots of sneezing and a runny nose: hay fever season has well and truly arrived, and with it the onslaught of symptoms that come from a spike in pollen levels.

For many people, this is a yearly occurrence – something that has come around time and time again since childhood. But for others, it’s more of a new thing. I’m one of these people. In fact, it wasn’t until I graduated from university at the age of 21 that I first started to suffer from the classic hay fever symptoms – in particular, an itchy nose and throat.

As someone who had never experienced allergies before, I was taken aback. I assumed hay fever was something that you either did or didn’t have – a condition that either emerged in childhood or never affected you. However, since those hay fever symptoms first came to the surface, they’ve not only stuck around but become worse with each passing year. Now, in 2024, I have to face hayfever season with an army of antihistamines and nasal sprays.

So, what’s the deal? Why do some people suddenly develop hay fever during adulthood? And does that mean the condition is with you for life? I put my questions to Dr Helen Evans-Howells, a GP and allergy specialist at Dr Helen Allergy. Here’s what she had to say. 

To understand why and how hay fever emerges, it’s a good idea to understand the basics of what hay fever is and how it affects the body. We all know it’s caused by different types of pollen in the atmosphere – but how does that lead to the tell-tale symptoms?

According to Dr Evans-Howells, it’s all to do with our bodies misinterpreting something that should be harmless – such as grass pollen or tree pollen – as something the immune system needs to attack, causing it to launch a reaction.

“When the body is then exposed to something like grass pollen, the immune cell immunoglobulin E (IgE) binds to the grass pollen on exposure and triggers a breakdown of the body’s mast cells,” she explains. A mast cell is a type of white blood cell, and it’s the breakdown of these cells which causes the typical ‘allergy’ response.”

She continues: “These cells contain chemicals such as histamine, and it is the histamine which is responsible for causing the blood vessels to dilate and swell. This results in the symptoms of a running nose, congestion, sneezing and itchy eyes. Some people will also develop rashes, breathing difficulties, headaches and fatigue.” 

If, like me, you were hoping for an explanation, Dr Evans-Howells has some bad news. For the most part, it’s not fully understood why some adults develop hay fever seemingly out of the blue.

“Hayfever generally develops in school-age children and beyond – it would be unusual for a baby to have hayfever and generally we do not see allergy tests become positive until around the age of three,” she explains.

“We don’t know why some people never develop symptoms until they are an adult, but with women particularly, it is common to see changes occur through life – especially at times of hormonal changes such as during pregnancy and menopause.”

Dr Evans-Howells adds: “If an adult develops hayfever symptoms in their 70s and has never had any atopic conditions (which would include eczema, environmental allergies, food allergies or asthma) then it would be highly unlikely that the symptoms are triggered by a pollen allergy.

“It’s much more likely that the nose and eye symptoms may be triggered by something else. These might include non-allergic rhinitis caused by medications or changes within the nose that occur as people get older or dry eye syndrome.” 

Again, experts aren’t totally clear on what can cause hay fever to disappear – but the good news is that it can. In fact, whether you develop hay fever as a child or as an adult, it can get better (or worse) from year to year, depending on a variety of factors.

For example, as a child, you might spend more time playing outside on grass (where grass pollen exposure is obviously going to be high) and therefore experience worse symptoms.

However, in some people, allergies can just disappear as they age. “The response from the immune system to reacquire tolerance to substances such as pollen and foods is not well understood,” Dr Evans-Howells acknowledges.

“We do know that immunotherapy can help to teach the immune system to stop being so responsive. Immunotherapy or desensitisation is when we expose the body to a constant amount of a substance it is allergic to – such as grass pollen – in the form of a drop, dissolvable tablet or injection.

“By exposing the body regularly to this substance for three years, the immune system can learn to be less reactive and, for some, this will mean that their allergies will resolve. However, the greatest benefit occurs when immunotherapy is given at a young age as the immune system is more modifiable.” 

While some people’s hay fever may not go away, symptoms do tend to vary between people – as well as varying in severity every year. But why is this? 

Recent changes in symptom severity are likely down to one key factor, Dr Evans-Howells explains. That factor? Climate change.

“Hay fever symptoms do seem to be getting more severe for most people with each passing year,” she says. “This is genuine and due to the increased pollen levels that are occurring in our country; with climate change, we are noticing longer pollen seasons and significantly increased levels of pollen which are affecting more people.”

As far as symptom difference between people goes, the cause is less clear, Dr Evans-Howells adds. “Just like asthma, hay fever symptoms can vary in severity from person to person. It is not clear why this is the case, but it is more likely that somebody who has multiple environmental allergies and asthma will have more significant symptoms than those who may only be allergic to one thing.”

She continues: “However, there is a significant degree of variation and the reasoning for this is not known. Additionally, the severity for one person can change year-to-year and, as I’ve said, hormones can influence the degree of symptoms someone has.” 

Images: Getty