How Much Antihistamine Can I Take In 24 Hours?

In this article, we'll provide you with a clear guide to antihistamines. We'll cover what antihistamines are used for, how they work and how much you can safely take within 24 hours. We'll also explain whether the dosage you take varies depending on the type of antihistamine, as well as practical tips to ensure you use them safely. We will also answer a number of frequently asked questions regarding antihistamines and their dosage.

Key Takeaways

Here are the 5 biggest takeaways from this article about how much antihistamine you can take in a 24-hour period:

• Antihistamines are primarily used to relieve allergy symptoms, including hay fever, hives, conjunctivitis, and reactions to insect stings and bites.

• The typical adult dose for many over-the-counter antihistamines is 10mg once daily. However, the appropriate dose can vary based on the specific product, age, weight and the severity of your symptoms.

• Dosage can differ between children and adults. Children's doses are often lower and depend on their age and weight.

• Different antihistamines have varying dosage instructions. For example, cetirizine and loratadine typically have a 10mg daily dose for adults, while chlorphenamine and fexofenadine have different dosing schedules and maximum limits.

• To use antihistamines safely, follow the recommended dosage, monitor for side effects, and consult a healthcare provider if you experience excessive drowsiness or other concerns.

What are antihistamines used for?

Antihistamines are commonly used to relieve symptoms of allergies such as hay fever, hives and conjunctivitis. They can also help with reactions to insect bites or stings. Beyond allergy relief, antihistamines are sometimes used to prevent motion sickness, manage nausea and vomiting and even as a short-term treatment for insomnia (NHS, 2023).

How many antihistamine can I take in 24 hours?

The amount of antihistamine you can take in 24 hours depends on the type of antihistamine you're using. For most over-the-counter antihistamines, the typical adult dose is 10mg once daily. However, this can vary depending on the specific product, age, weight and how severe your symptoms are. It's important to always follow the dosage instructions on the packaging or consult a healthcare professional if you're unsure (McDougall, 2024).

Is the dose of antihistamine different for children and adults?

Yes, the dose of antihistamines can be different for children and adults. For children, the dosage is often lower and may vary depending on their age and weight. It's important to speak to a pharmacist or GP if you are looking at antihistamines for your children as some antihistamines may not be suitable for them. The same applies if you are pregnant, breastfeeding, an older person, or have an underlying health condition such as heart, liver, or kidney disease (NHS, 2023).

Is dosage different for different types of antihistamines?

Cetirizine (Allacan, Benadryl Allergy, Piriteze Allergy, Zirtek Allergy)

Yes, the dosage can vary depending on the type of antihistamine you're taking. For example, the usual dose of cetirizine (the active ingredient in antihistamine medications such as Allacan, Benadryl Allergy, Piriteze Allergy and Zirtek Allergy) for adults is 10mg once a day. However, if you have kidney problems, the recommended dose is often lower (NHS, 2021).

Chlorphenamine (Piriton, Allerief, Hayleve, Pollenase)

Another popular antihistamine medication is chlorphenamine. This is the active ingredient in products such as Piriton, Allerief, Hayleve and Pollenase. The usual dose of chlorphenamine for adults and children aged 12 years and older is one tablet every 4 to 6 hours, with a maximum of 6 tablets in 24 hours (NHS, 2021).

Fexofenadine (Almerg, Telfast, Treathay)

Fexofenadine is another antihistamine medication that is sold under the brand names Almerg, Telfast and Treathay. The dose you take will depend on what you're treating. For hay fever, adults and children aged 12 and over typically take 120mg once a day, while children aged 6 to 11 usually take 30mg twice a day, with doses spaced 10 to 12 hours apart (NHS, 2021). 

Loratadine (Clarityn)

Loratadine is a commonly used antihistamine and is sold under the brand name Clarityn. The typical adult dose of loratadine is 10mg once a day, but people with liver problems usually need a lower dose. For children, the dose is determined based on their weight or age (NHS, 2021).

Tips For Taking Antihistamines Safely

Ensuring you remain safe when you use any medication is important, even with over-the-counter products like antihistamines. Here are some tips you can follow to help you take antihistamines safely, according to the NHS:

• Always take your antihistamine exactly as advised by your pharmacist or doctor, or as described in the medicine's leaflet.

• Make sure you know the correct dose for your age, weight, and condition. If you are not sure you should consult with a pharmacist, doctor, or the patient information leaflet.

• Keep a log of when you take your antihistamine, the dosage, and any side effects you experience.

• Some antihistamines are best taken before bedtime, especially if they cause drowsiness. Others may need to be taken at specific times during the day.

• If you experience side effects like excessive drowsiness, dry mouth, or anything unusual, consult your pharmacist or doctor.

• If you have an underlying condition, such as liver or kidney disease, or if you’re pregnant, breastfeeding, or taking other medications, speak with your doctor or pharmacist before taking an antihistamine.

• If you miss a dose, follow the instructions in the leaflet or ask a pharmacist for advice.

Antihistamine FAQs

Is it dangerous to take 3 antihistamines at the same time?

Yes, taking three doses of an antihistamine at the same time can be dangerous and may lead to an overdose. Antihistamines are usually meant to be taken once every 24 hours, and exceeding the recommended dose can increase the risk of serious side effects, such as extreme drowsiness, confusion, or even more severe reactions like an overdose. 

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

For most over-the-counter antihistamine products, it is generally safe to take only one pill per 24-hour period. Taking two doses within such a short time frame can increase the risk of adverse effects, such as extreme drowsiness or other side effects.

What is the proper amount of antihistamines that I should take in a day?

For many common over-the-counter antihistamines, the typical dose for adults is 10 mg taken once a day. However, the exact dosage can vary depending on the specific product, your age, weight and the severity of your symptoms. It is crucial to follow the dosage instructions in the patient information leaflet or provided by your healthcare provider.

Is it safe to take 10mg of antihistamine?

Yes, 10mg is a common and generally safe starting dose for many popular over-the-counter antihistamines in the UK, such as cetirizine and loratadine. Your dosage will depend on the particular product you have, your specific condition, your age and other factors. If you do not know the dosage you should be taking it is important to consult with a healthcare provider or the information provided in the patient information leaflet.

Sources

Antihistamines - NHS

Cetirizine: antihistamine that relieves allergy symptoms - NHS

Loratadine (Clarityn): antihistamine that relieves allergy symptoms - NHS

Fexofenadine: antihistamine that relieves allergy symptoms - NHS

Chlorphenamine: drowsy (sedating) antihistamine - NHS