The Independent Pharmacy

How Much Antihistamine Should You Take? Brand Guide

Scott McDougall
Scott McDougallMPharmDirector & Registered Manager

Reviewed on 7 May 2024

How much antihistamine should you take?

For most over-the-counter options, the typical adult dose is 10mg once daily. However, the exact amount can vary depending on the specific product, your age, weight, and symptom severity.

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Benadryl Allergy One-A-Day Tablets
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For example, with cetirizine (found in brands like Zirtek, Piriteze and Benadryl), most adults can take 10mg once a day. But children’s doses are lower, and elderly patients may need to start with just 5mg. Loratadine (Clarityn) is another allergy medication taken as a 10mg tablet once a day. It's good for treating hay fever and doesn't usually make you feel sleepy.

Piriteze Allergy Tablets
Piriteze Allergy Tablets
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The key is choosing the antihistamine type and dosage that provides maximum relief with minimal side effects for your situation.

Let’s dive deeper into dosing guidelines for some of the most popular hay fever tablets.

Key Takeaways

  • For cetirizine (Zirtek, Benadryl, and Piriteze), the typical adult dose is 10mg once daily, but dosages decrease for children under 12.
  • Loratadine (Clarityn) is another well-tolerated 10mg once-daily option, good for non-drowsy allergy relief.
  • The dose for Fexofenadine (found in Treathay, Telfast) can be between 120mg and 180mg per day, depending on how severe your allergies are.
  • Chlorphenamine (Piriton) can make you more sleepy than other hay fever medications, so it is usually taken in smaller amounts—4mg every 4 to 6 hours by adults.
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Dosage Guidelines for Popular Antihistamine Brands

Cetirizine (Zirtek, Benadryl, and Piriteze)

For most adults and children over 12, the recommended cetirizine dose is 10mg once daily according to the NHS. This non-drowsy antihistamine works by blocking the effects of histamine (the chemical in your body that causes allergic reactions) in the body to provide 24-hour relief from sneezing, itchy/watery eyes, runny nose, and skin rashes.

For children between 6-12 years old, the dose is typically 5mg once a day. And for little ones between 2-6 years, only 2.5mg per day is advised unless otherwise directed by your paediatrician.

What is the best time to take hay fever tablets like cetirizine? It’s best to take cetirizine with a full glass of water on an empty stomach, either in the morning or before bed. If you miss a dose, there’s no need to double up - just take your regular amount as soon as you remember.

Based on a 2023 study, some minor side effects like headache or dry mouth are possible. If you experience severe dizziness, trouble breathing, or an irregular heartbeat, discontinue use and seek medical attention immediately. However, these reactions are rare.

Loratadine (Clarityn)

A 10mg tablet of loratadine once daily is the go-to dosage for most adults with hay fever, hives, or other allergy symptoms. Since it’s a non-drowsy formula, you can take it anytime without worrying about grogginess.

For children ages 6-12, the loratadine dose that the NICE recommends drops to 5mg once a day. And little ones between 2-6 years old should only take 2.5mg unless directed otherwise by their doctor.

Loratadine is absorbed better when taken with food or a drink. And if you have liver problems, you may need a lower dose, so check with your pharmacist.

Don’t drive or operate heavy machinery until you know how this medication will affect you. Contact your doctor if hay fever symptoms persist for more than a few days despite taking loratadine regularly.

Compare it with other options like Desloratadine in our guide on Desloratadine vs. Loratadine.

Fexofenadine (Treathay and Telfast)

For seasonal allergy relief, the standard fexofenadine dose recommended by the NHS is 120mg once daily for adults and children over 12 years old. If you’re dealing with more persistent, year-round allergies, the dose may be increased to 180mg per day.

It’s important to take fexofenadine (also available as branded versions called Treathay and Telfast) with water on an empty stomach at least one hour before or two hours after a meal or snack. Food can decrease how much of the medication your body absorbs.

During peak pollen seasons or times of high exposure, some patients may need an added 60mg dose in the evening for better 24-hour coverage. But don’t adjust your dosage without consulting your doctor or pharmacist first.

Children under 12 usually need smaller doses, which are calculated based on their weight. Your child's doctor can tell you the right amount.

Chlorphenamine (Piriton)

As an older, first-generation antihistamine, chlorphenamine (also available as Piriton) is known to cause more sedation than newer products, which is why doctors recommend taking it at night. The standard adult dose of chlorphenamine reccomended by the NHS is 4mg every 4-6 hours, up to 24mg per day.

For children ages 6-12, the dose drops to 2mg every 4-6 hours, maxing at 12mg daily. Little ones aged 1-5 can take 1mg every 4-6 hours but no more than 6mg per day.

Elderly patients and those with liver or kidney issues may need to start with lower chlorphenamine doses due to the increased risk of side effects. Be sure to discuss your complete medical history with your doctor or pharmacist.

Take this medication with water, milk or food to minimise stomach upset. Avoid activities requiring mental alertness until you know how it affects you, as drowsiness is common.

Tips for Safe Antihistamine Use

A 2022 study in the World Allergy Organization Journal confirms that antihistamines are generally safe when taken as directed. But it’s still important to pay close attention to how your body responds. Keep a log of the specific product, dosage, time taken, and any symptoms or side effects you experience.

If you don't see an improvement in your allergies after several days, it's possible the medication isn't the right strength for you. It's important to find what works best for you, and we're here to help with that. On the flip side, if you feel excessively drowsy, have a dry mouth, or have other worrying effects, you may need to lower your dose.

Don't change the amount of allergy medicine you take without first talking to your doctor or pharmacist. They can review your log, assess potential interactions with other medications, and recommend the ideal next steps.

Take the Next Step with The Independent Pharmacy

Now that you understand more about safe, effective antihistamine dosing, it’s time to take control of your hay fever symptoms, even when you're on holiday!

A quick self-assessment on our website can help pinpoint which treatment options could work best for you.

Just answer a few simple questions about your age, allergy history, and current symptoms of allergies. Then, our team of certified experts will review your responses and recommend specific over-the-counter or prescription-strength antihistamine products and dosages tailored to your needs. Once we’ve reviewed your case, we’ll provide a list of the right treatments for you.

Getting ahead of hay fever season has never been easier! Plus, our online consultations are completely free and confidential. No more waiting weeks for an appointment or wasting money on trial-and-error medications.

If you want to learn more about your condition, read our hay fever guides, which cover everything from different medications to how long hay fever tablets take to work.

You shouldn't have to suffer because of your allergies. Get in touch with our team and let us help you take control with treatments that are tailored specifically for you at The Independent Pharmacy. You deserve to live comfortably and free from allergy symptoms.


What is the proper intake of antihistamines?

For many common allergy pills available without a prescription, the usual dose for adults is 10 milligrams (mg) taken once a day. However, this can vary based on the specific product, your age, weight, and severity of symptoms. Always follow dosage instructions carefully.

Is 10mg antihistamine a lot?

No, 10mg is a common and safe starting dose for many popular over-the-counter antihistamine brands in the UK, like cetirizine (Zirtek) or loratadine (Clarityn). Higher doses may be needed in some cases but should only be taken under medical supervision.

Is 3 antihistamines too much?

Yes, taking three doses of an antihistamine at once could potentially cause an overdose situation. Never take more than the recommended single dose, and space out doses per product instructions (usually once every 24 hours).

Is it OK to take 2 allergy pills in 24 hours?

For most over-the-counter antihistamine products, it’s generally safe to take only one pill per 24-hour period. Taking two doses so close together increases your risk of adverse effects like extreme drowsiness. Always space out doses as directed on the label.


NHS (2021). Cetirizine -

NICE (2024). Loratadine -

NHS (2021). Fexofenadine -

NHS (2021). Chlorphenamine -

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