Around one in four people in the UK suffer from hay fever – a seasonal allergy that can wreak havoc with daily life, causing uncomfortable symptoms such as sneezing, itchy eyes and blocked sinuses.
But while millions turn to over-the-counter or prescription antihistamines for relief, experts warn the tablets could have an unexpected side effect.
With parts of England experiencing high pollen counts this week, a GP has revealed that long-term use of some antihistamines may increase appetite – potentially leading to extra pounds over time.
‘Histamine actually helps suppress appetite in the brain,’ explains Dr Crystal Wyllie, a GP at ZAVA Online Doctor.
‘When you take an antihistamine, you’re blocking that effect, which may make you feel hungrier than usual. Over time, that can lead to increased calorie intake without you even realising it.’
Histamine is best known as the chemical the body releases during an allergic reaction to triggers such as pollen, dust or pet hair.
But it also plays an important role in regulating wakefulness and hunger.
By interfering with this process, antihistamines may subtly shift how the body controls appetite.
Millions of people with pollen allergies turn to antihistamines for relief during hay fever season
There are two main types of antihistamines: older sedating antihistamines like chlorphenamine, commonly sold under the brand name Piriton.
Newer, non-drowsy options like acrivastine are often sold under the brand name Benadryl Allergy Relief.
Other common, non-drowsy alternatives include Piriteze (cetirizine) and Clarityn (loratadine).
However, even modern formulations may still influence appetite, while older types can also cause drowsiness, reducing physical activity and further contributing to gradual weight gain.
Research suggests the link may be more than anecdotal. One observational study found children taking antihistamines saw their body mass index (BMI) percentile rise by an average of 1.17 points per year, compared with a slight decrease in those not taking the medication.
Another study in 2020 found people using prescription antihistamines tended to have higher body weight, BMI and insulin levels than those who did not.
Experts stress the relationship is complex.
‘Weight and allergies appear to be linked in a two-way relationship,’ says Dr Wyllie.
‘It’s important to look at the bigger picture rather than blaming a single medication.’
They also emphasise that antihistamines remain a safe and effective treatment, and any weight changes are likely to be modest and vary between individuals.
But for those concerned about the potential side effects, small lifestyle tweaks – including diet – may help manage symptoms more holistically.
‘Food isn’t a replacement for medication, but certain nutrients can help your body respond more calmly to allergens,’ Dr Wyllie explains.
‘Think of it as supporting your system from the inside out.’
Ingredients such as ginger and turmeric are known for their anti-inflammatory properties, which may help ease irritation in the airways.
Citrus fruits – including oranges and lemons – are rich in vitamin C, a natural antihistamine, while onions and apples contain quercetin, a plant compound thought to help stabilise the cells that release histamine.
Adding more oily fish such as salmon and mackerel to your diet may also help reduce inflammation thanks to their omega-3 fatty acid content.
There is also some evidence – though not conclusive – that consuming local honey could help the body build tolerance to pollen over time.
On the flip side, highly processed foods, excess sugar and alcohol can increase inflammation, potentially making hay fever symptoms feel worse.
Experts say managing hay fever effectively often requires a combination of medication, lifestyle changes and diet rather than relying on a single solution.
And while antihistamines may help keep sneezing at bay, being mindful of their wider effects, including appetite, could help prevent the scales from creeping up.
