I’m a pharmacist – here’s the truth about taking more than one antihistamine a day

ANTIHISTAMINES are a hay fever sufferer’s lifeline in the summer months.

The daily pill relieves a whole host of symptoms, from itchy eyes to a streaming nose. 

There are dozens to choose from – chlorphenamine, cetirizine and fexofenadine all fall under antihistamines and are some of the most popular choices.

Superintendent Pharmacist, Phil Day, explained how they work.

He told The Sun: “When your body comes into contact with allergens like pollen, your body can respond to it by producing a chemical called histamines. 

“Histamines cause swelling and expansion of the blood vessels, which is the root of most hay fever symptoms. 

“Antihistamines work by blocking histamines, so you should notice a decrease in swelling, itching, and other symptoms when you take them.

“Frequent sufferers may find regular treatment more beneficial to keep the symptoms at bay. For more severe cases, prescription strength antihistamines may be required.”

According to Chemist4U, some 65 per cent of people with hay fever globally rely on antihistamines.

And GPs in Bridgend, Wales, prescribe the highest amount of antihistamines compared to anywhere else in the UK.

But as the pollen count soars across the UK this week, many people will be wondering the same thing.

Can you take more than one antihistamine in a day, and what’s the worst that could happen?

Phil said: “You should always check the label of your medication to ensure you are taking the correct dosage.

“If you’re a healthy adult and take more than the daily recommended dose, you probably won’t experience many negative side effects.

“However, larger overdoses can be a lot more serious, especially in children.  

“If you think you have taken too many antihistamines, it’s best to seek professional medical help, as overdose symptoms can take a while to kick in.”

Some antihistamines cause drowsiness (such as chlorphenamine (Piriton), cinnarizine, diphenhydramine, hydroxyzine and promethazine).

Other side effects include a dry mouth, blurred vision and headaches.

Symptoms of an overdose – which can be life-threatening, as with any medicine – include increased drowsiness, blurred vision, nausea, vomiting, increased heart rate, confusion and loss of balance.

With the non-drowsy forms of antihistamine, an overdose would be less severe, Healthline reports.

It may cause dizziness, a headache, drowsiness and agitation.

People have died from taking too many antihistamines because they have suffered complications such as cardiac arrest due to a rapid heart rate.

Researchers warned in a 2021 paper that antihistamine deaths were increasing in England, due to the rise in their popularity. 

It’s always important to read the packaging of your antihistamines.

Phil added: “Taken in their recommended dose, antihistamines are fine to take regularly but you should discuss with your pharmacist or GP before taking them for a prolonged period of time.”

When should you take your antihistamine?

Given antihistamines should be taken just once per day, when is the best time of day to take them?

Some swear by them in the morning, while others take them before bed to wake up feeling refreshed.

The NHS says the leaflet will tell you when to take it, as some types are best before bedtime.

MedlinePlus reports: “For many people with allergies, symptoms are the worst around 4 a.m. to 6 a.m. 

“Taking an antihistamine at bedtime may help you or your child feel better in the morning during allergy season.”