Approximately one in four individuals in the UK grapple with hay fever, a seasonal allergy that can significantly disrupt daily activities. This common ailment is notorious for causing a suite of bothersome symptoms, including relentless sneezing, itchy eyes, and blocked sinuses.

While many sufferers reach for over-the-counter or prescription antihistamines to alleviate these discomforts, experts caution that these medications might come with an unforeseen downside. In light of the high pollen counts sweeping across parts of England this week, new insights have emerged regarding the long-term use of certain antihistamines.

Dr. Crystal Wyllie, a general practitioner with ZAVA Online Doctor, sheds light on the situation: “Histamine plays a role in suppressing appetite in the brain. When you take an antihistamine, it blocks this effect, potentially making you feel hungrier than usual. Over time, this may lead to an increased calorie intake without you even noticing.”

Histamine is primarily recognized as the chemical the body releases during an allergic reaction to triggers like pollen, dust, or pet dander. However, its role in appetite regulation introduces a new dimension to the conversation about antihistamine use and its possible implications on weight.

‘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.