Deborah Bartlett never understood what people meant when they talked about hay fever ruining their lives every summer until she developed it herself in her late 20s.

'Then it hit me', she admits. 'All of a sudden I was constantly sneezing, my nose was streaming, and my eyes were so itchy it was unbearable.'

Deborah's misery would start in the spring and last all through the summer. 'The worst element was how itchy my eyes were, especially because I wore contact lenses,' she says.

She tried every over-the-counter medication available – from nasal sprays to tablets and eye drops – but nothing seemed to help.

She'd resigned herself to never seeing the back of her symptoms until she 'stumbled across something completely by accident that finally brought my symptoms under control', says Deborah, 61, an interior design journalist who lives in West Sussex, with her husband.

Her daughter, Katie, 35, had accidentally left a bottle of liquid probiotics – 'friendly bacteria' – at Deborah's home in March 2023.

The probiotic contains four strains of live bacteria and Katie had been taking it to help boost her health during a difficult pregnancy.

'I'd never really had any concerns about my gut health and hadn't felt the need to take a probiotic,' says Deborah. 'I'm fit, eat well and generally look after myself but I thought I'd give it a go rather than let it go to waste.

'I started taking a 70ml shot every day, as per the instructions, and noticed I had a bit more energy. So I bought some more and carried on taking it.'

She was not expecting it to help with her hay fever and didn't realise anything had changed until the following spring when, as Deborah says: 'People started talking about their allergies and I suddenly thought: "Hang on a minute, I haven't had hay fever!"'

'There was no streaming nose, no relentless sneezing and no desperately itchy eyes. It was completely unexpected.'

In fact there is 'an emerging body of evidence suggesting that certain types of bacteria, particularly Lactobacilli and Bifidobacteria – often referred to as "friendly bacteria" – may be a useful addition to treatment to allergies such as hay fever', says Adam Fox, a consultant at the Allergy London clinic.

Which could be welcome news for some of the estimated 16million hay fever sufferers who annually battle symptoms ranging from fatigue and brain fog to itchy eyes and persistent sneezing.

This year many have found their symptoms are being made worse by unpredictable weather, high temperatures and thunderstorms which can all impact how much pollen is released and how long it stays airborne. In fact, the NHS reported that visits to its hay fever advice page more than doubled in a week amid the recent hot spell.

Known medically as seasonal allergic rhinitis, hay fever occurs when the body's immune system overreacts to harmless pollen, releasing high levels of a chemical called histamine in an attempt to fight off what it mistakenly perceives to be an invader. It is the effects of histamine that cause inflammation in the nasal passages, and blood vessels in the eyes to dilate, resulting in symptoms such as sneezing, a blocked or runny nose, and itchy, watery eyes – it's the body trying to get rid of the 'invader'.

But now there is emerging research that the gut – which is home to trillions of microbes known as the microbiome, maybe involved too, says Professor Fox, who is also chair of the National Allergy Strategy Group, an alliance of allergy professionals and organisations campaigning to improve allergy services across the NHS.

In fact a 2025 study, published in Frontiers in Microbiology, suggested an imbalance in gut bacteria can directly disrupt the immune system leading to hay fever.

So could taking probiotics be the answer?

It's thought that probiotics might help to ease hay fever symptoms because changing the balance of bacteria in the gut can increase the beneficial compounds produced by certain gut bacteria, explains Professor Fox.

'When certain gut bacteria break down fibre, they produce short-chain fatty acids – particularly butyrate – which can have an anti-inflammatory effect that may help allergic conditions such as hay fever,' he says.

In a 2022 Australian study, adults who took a probiotic for 10-12 weeks reported fewer hay fever symptoms, including runny noses and itchy eyes, as well as an improved quality of life compared with those who were given a placebo.

A 2017 trial by researchers at the University of Florida also found that hay fever sufferers who took a three-strain probiotic had a significantly improved allergy-related quality of life during pollen season, compared with those who took a dummy treatment.

The evidence so far suggests that taking probiotics alongside standard hay fever treatments is the most beneficial strategy – 'it's a harmless intervention and a reasonable thing to try', says Professor Fox.

However, he stresses that for those with 'severe hay fever, taking probiotics alone is unlikely to be enough'.

While bigger trials are needed to determine how much of a benefit probiotics might be to at least some of those with hay fever, Helen Brough, a consultant in paediatric allergy who is on the advisory board for the charity Allergy UK says: 'The science is moving in a very positive direction and I find it one of the most hopeful areas in allergy medicine today.'

It's thought that other types of allergies might benefit - with probiotics potentially being used to change the make-up of bacteria in the gut which in turn bring about changes in the immune system 'as a way of helping to manage allergic conditions in people who already have them, rather than trying to prevent allergies from developing in the first place', says Professor Fox, who is also an allergy consultant at a leading London NHS teaching hospital.

'I think we are at the beginning of a genuinely exciting shift in how we understand and treat allergies,' adds Professor Brough.

'Rather than simply suppressing symptoms with antihistamines, future allergy care may well involve profiling a patient's gut microbiome and prescribing targeted probiotic therapies to help restore tolerance from within.'

Deborah meanwhile is adamant that it is the probiotics that helped her.

She developed hay fever after moving to Melbourne, Australia in 1984 to work with Vogue Living interiors magazine and found standard antihistamines of little help.

'Melbourne is known for being one of the world's hay fever hotspots because of its unique mix of grasses and pollens, and I think that's what sensitised me,' she says.

'I wore contact lenses and played a lot of tennis, so being outside made it even worse. My eyes were so itchy and inflamed that I used to joke that I wanted to scratch them with a fork.'

Deborah tried all kinds of over-the-counter remedies but although eye drops would 'take the edge off' the itching and streaming, nothing made a significant difference.

It made her life an annual misery, ruining countless summer weddings and parties.

'I was also doing some broadcasting work at the time – covering the Australian Open tennis for radio. I'd be sitting in the court-side press seats hoping I could do my live crosses without spluttering too obviously.'

She hoped that when she returned to the UK in 2015 her symptoms would improve but they didn't.

'Every spring I'd brace myself for months of sneezing, itchy eyes and misery,' she says.

Then she tried the probiotics, a brand named Symprove.

Professor Fox cautions that: 'Many people who suffer badly with hay fever find that their symptoms will naturally improve as they get older, regardless of any treatment they're taking.'

He also points to other developments that have significantly improved the lives of those with severe hay fever – in particular, desensitisation therapy, which involves taking a small dose of the pollen causing the allergy under the tongue each day or regular injections of an allergen in a clinic. Though they don't work for everyone, both have proved transformative for many suffering with hay fever. 'We are pushing hard to improve patient access to these treatments,' he says.

However, Deborah is convinced it was the probiotic that helped her: 'I wasn't doing anything different with my diet or lifestyle. It seems too much of a coincidence that I've now been hay fever-free for the three years I've been taking it,' she says.

'This year has been particularly lovely because we have a new puppy and I've been able to play with her in the garden, sit on the grass and enjoy being outdoors without worrying about allergies,' she says.