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Benadryl vs. Zyrtec: How These Common Allergy Medications Compare

Written by Andrew Le, MD

UpdatedFebruary 29, 2024

When suffering from allergies, two of the most common over-the-counter medications people turn to are Benadryl and Zyrtec. Both drugs are antihistamines, meaning they block the action of histamine, a chemical released by the body during an allergic reaction.

However, understanding some critical differences between these drugs is essential when determining which one to use.

This article provides a head-to-head comparison of the antihistamines Benadryl and Zyrtec. It examines how they work, their effectiveness in treating allergy symptoms, standard dosages, potential side effects, costs, and recommendations from medical guidelines.

🔑 Key Takeaways

  • Benadryl is a first-generation antihistamine that readily crosses into the brain, leading to increased sedation, while Zyrtec selectively targets peripheral histamine receptors with less sedative effects.
  • Although Benadryl and Zyrtec have similar efficacy in treating allergies, guidelines prefer Zyrtec due to its longer duration of action and better safety profile than Benadryl.
  • The standard dosage is 25-50 mg every 4-6 hours as needed for Benadryl and 10 mg once daily for Zyrtec in most adults and children over age 12.
  • Common side effects of Benadryl include dizziness, drowsiness, dry mouth, blurred vision, and constipation, while Zyrtec may cause nausea, headache, dizziness, and mild drowsiness.
  • Benadryl has more anticholinergic effects like dry eyes, dry throat, and constipation versus Zyrtec's less drying side effects. Both can rarely prompt severe allergic reactions.
  • A 24-tablet pack of Benadryl costs about $10, while 14 tablets of Zyrtec are around $22; generics and discount programs can reduce costs.
  • The price-checker Cuverd® utilizes superior search technology to uncover the best prescription medication discounts available.
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1. Mechanism of Action

Antihistamines like Benadryl and Zyrtec work by blocking the effects of histamine, a chemical released during allergic reactions. However, critical differences in their mechanisms of action impact their safety and side effect profiles.

Benadryl

Benadryl is an antihistamine that belongs to the first-generation antihistamine class. The primary mechanism of action of diphenhydramine involves blocking the effects of histamine, a natural chemical produced by the body in response to allergens. Histamine is responsible for triggering symptoms during allergic reactions such as:

As a first-generation antihistamine, Benadryl readily crosses the blood-brain barrier and acts on central nervous system (CNS) histamine receptors. By binding to and inhibiting these receptors, diphenhydramine mitigates the effects of histamine in the brain, leading to its sedative and drowsiness-inducing properties. This CNS depression is why Benadryl is often used not only for allergies but also for its sedative effects in treating insomnia and motion sickness.

Moreover, Benadryl exhibits anticholinergic properties, blocking the action of acetylcholine, another neurotransmitter. This contributes to its side effects, such as dry mouth, constipation, and blurred vision.

Zyrtec

Zyrtec is a second-generation antihistamine, and its primary active ingredient is cetirizine. Unlike first-generation antihistamines like Benadryl, cetirizine has a more selective action on peripheral H1 receptors, primarily located in the tissues rather than the CNS. This results in reduced penetration of cetirizine into the brain, leading to a lower incidence of sedation and drowsiness compared to first-generation antihistamines.

The main mechanism of action of Zyrtec involves blocking the effects of histamine at the peripheral H1 receptors. By inhibiting histamine binding, cetirizine prevents or alleviates allergy symptoms, including:

  • Sneezing
  • Itching
  • Runny nose

Cetirizine does not readily cross the blood-brain barrier significantly, reducing the likelihood of sedative effects. While it may still cause mild drowsiness in some individuals, this is generally less pronounced than first-generation antihistamines.

2. Efficacy In Treating Allergy Symptoms

A study found that Zyrtec and Benadryl displayed comparable efficacy and onset of action, with the added benefit of Zyrtec having a longer duration of action. This implies that Zyrtec may provide sustained relief over a longer period than Benadryl.

Additionally, a literature review comparing Benadryl to non-sedating antihistamines, such as Zyrtec, emphasized that all antihistamines shared similar effectiveness. However, the review highlighted a key advantage of newer antihistamines like Zyrtec, which is their tendency to cause less sedation compared to traditional options like Benadryl.

The Canadian Society of Allergy and Clinical Immunology (CSACI) recommendations further support the preference for Zyrtec over Benadryl. According to the CSACI, newer antihistamines like Zyrtec are considered safer, less sedating, and more effective. They caution against the potential side effects associated with Benadryl, including sedation, impaired sleep, and motor impairment, which could lead to accidents and, in extreme cases, even death. The CSACI suggests that Benadryl should only be utilized as a last resort.

3. Dosage and Administration

Proper dosage is key for antihistamines to provide effective allergy relief while minimizing side effects.

Benadryl

Benadryl is available in various forms, such as:

  • Tablets
  • Capsules
  • Liquid

For adults and children aged 12 years and older, the usual dose ranges from 25 to 50 mg every four to six hours, as needed. It can be taken with or without food, but some may take it primarily at bedtime due to its potential to cause drowsiness.

For children under 12 years, the specific weight-based dose should be determined in consultation with a healthcare provider.

The liquid form should be measured using the dosing syringe or a special dose-measuring device. Motion sickness may be addressed by taking Benadryl 30 minutes before the triggering situation, and as a sleep aid, it is recommended within 30 minutes before bedtime.

In case of a missed dose, it can be taken as soon as remembered. However, extra medicine is not advised to make up for a missed dose.

Zyrtec

Zyrtec is available in tablets and liquid.

For adults and children 6 years and older, the standard dose is 10 mg once daily, with the option to take it with or without food.

Children aged 6 months to 2 years may start with an initial dose of 2.5 mg once daily, with a maintenance dose of 2.5 mg once to twice daily, not exceeding 5 mg daily. For children aged 2 to 5 years, the initial dose is 2.5 mg once a day, with a maintenance dose of 2.5 mg twice a day or 5 mg once daily, with a maximum of 5 mg per day.

For children aged 6 years and older, the dose is 5 to 10 mg once a day, not exceeding 10 mg per day.

Zyrtec can be taken with or without food; chewable tablets should be chewed before swallowing. Orally disintegrating tablets should be allowed to dissolve in the mouth without chewing.

If a dose is missed, skipping it rather than two doses at once is recommended.

4. Side Effects

While antihistamines treat allergies, they may prompt side effects ranging from mild to severe.

Benadryl

Common side effects of Benadryl may include:

  • Dizziness
  • Drowsiness
  • Loss of coordination
  • Dry mouth, nose, or throat
  • Upset stomach
  • Constipation
  • Dry eyes
  • Blurred vision
  • Daytime drowsiness or a "hangover" feeling after nighttime use

More severe side effects that require immediate medical attention consist of signs of an allergic reaction, such as:

  • Hives
  • Difficulty breathing
  • Swelling of the face, lips, tongue, or throat

Contacting a doctor is necessary if experiencing:

  • Pounding heartbeats or fluttering in the chest
  • Painful or difficult urination
  • Little or no urination
  • Confusion
  • Feeling like they might pass out
  • Tightness in the neck or jaw with uncontrollable movements of the tongue
See prices for Benadryl on Amazon

Benadryl

Benadryl is available in various forms, such as:

  • Tablets
  • Capsules
  • Liquid

For adults and children aged 12 years and older, the usual dose ranges from 25 to 50 mg every four to six hours, as needed. It can be taken with or without food, but some may take it primarily at bedtime due to its potential to cause drowsiness.

For children under 12 years, the specific weight-based dose should be determined in consultation with a healthcare provider.

The liquid form should be measured using the dosing syringe or a special dose-measuring device. Motion sickness may be addressed by taking Benadryl 30 minutes before the triggering situation, and as a sleep aid, it is recommended within 30 minutes before bedtime.

In case of a missed dose, it can be taken as soon as remembered. However, extra medicine is not advised to make up for a missed dose.

See prices of Zyrtec on Amazon

Zyrtec

Zyrtec is available in tablets and liquid.

For adults and children 6 years and older, the standard dose is 10 mg once daily, with the option to take it with or without food.

Children aged 6 months to 2 years may start with an initial dose of 2.5 mg once daily, with a maintenance dose of 2.5 mg once to twice daily, not exceeding 5 mg daily. For children aged 2 to 5 years, the initial dose is 2.5 mg once a day, with a maintenance dose of 2.5 mg twice a day or 5 mg once daily, with a maximum of 5 mg per day.

For children aged 6 years and older, the dose is 5 to 10 mg once a day, not exceeding 10 mg per day.

Zyrtec can be taken with or without food; chewable tablets should be chewed before swallowing. Orally disintegrating tablets should be allowed to dissolve in the mouth without chewing.

If a dose is missed, skipping it rather than two doses at once is recommended.

4. Side Effects

While antihistamines treat allergies, they may prompt side effects ranging from mild to severe.

Benadryl

Common side effects of Benadryl may include:

  • Dizziness
  • Drowsiness
  • Loss of coordination
  • Dry mouth, nose, or throat
  • Upset stomach
  • Constipation
  • Dry eyes
  • Blurred vision
  • Daytime drowsiness or a "hangover" feeling after nighttime use

More severe side effects that require immediate medical attention consist of signs of an allergic reaction, such as:

  • Hives
  • Difficulty breathing
  • Swelling of the face, lips, tongue, or throat

Contacting a doctor is necessary if experiencing:

  • Pounding heartbeats or fluttering in the chest
  • Painful or difficult urination
  • Little or no urination
  • Confusion
  • Feeling like they might pass out
  • Tightness in the neck or jaw with uncontrollable movements of the tongue

⚠️ Warning

Specific considerations for older adults include a higher likelihood of experiencing side effects.

Zyrtec

Common side effects of Zyrtec may include:

  • Nausea
  • Vomiting
  • Diarrhea
  • Cough
  • Drowsiness
  • Tiredness
  • Headache
  • Dizziness
  • Feeling light-headed
  • Feeling hot
  • Sweating
  • Numbness, tingling, burning pain
  • Altered sense of taste
  • Upset stomach
  • Constipation
  • Dry mouth
  • Sore throat
  • Nosebleed
  • Dry eyes

While drowsiness is a common side effect, Zyrtec tends to cause less drying side effects when compared to Benadryl like:

  • Dry eyes
  • Dry throat
  • Constipation
  • Urinary retention

In cases of an allergic reaction to Zyrtec, individuals may experience:

  • Hives
  • Difficulty breathing
  • Swelling of the face, lips, tongue, or throat

Severe symptoms that warrant immediate medical attention include overdose symptoms such as:

  • Severe drowsiness
  • Vision problems
  • Agitation
  • Fast heartbeats
  • Stomach pain
  • Nausea
  • Vomiting
  • Trouble walking
  • Trouble swallowing or speaking

❤️‍🩹Health Note

Activities requiring alertness should be avoided until the effects of Zyrtec are known, and alcohol consumption should be approached with caution.

5. Cost

The price tag of medications may influence medication access and adherence. Options exist to reduce costs.

Benadryl

The cost for a Benadryl oral tablet of 25 mg is around $10 for a supply of 24 tablets, depending on the pharmacy you visit. Additionally, a generic version of Benadryl is available at a starting price of $11.14 for 24 tablets.

The prices are quoted for cash-paying customers and are not valid with insurance plans. It's worth noting that Benadryl offers may include printable coupons, rebates, savings, copay cards, trial offers, or free samples through programs like the Drugs.com Discount Card, which can save users up to 80% or more off the cost of prescription medicines.

Zyrtec

Zyrtec tends to be pricier than Benadryl. The cost for a Zyrtec oral tablet of 10 mg is around $22 for a supply of 14 tablets. While a generic version of Zyrtec is available at a starting price of $10.94 for 30 tablets, it is still relatively more expensive than the generic version of Benadryl.

Like Benadryl, Zyrtec offers may include printable coupons, rebates, savings, copay cards, trial offers, or free samples through programs like the Drugs.com Discount Card.

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Wrap Up

While both Benadryl and Zyrtec effectively treat allergy symptoms through antihistamine effects, Zyrtec is typically preferred and recommended by guidelines due to its longer duration, once-daily dosing convenience, and reduced sedation compared to Benadryl.

Although it has a higher cost, Zyrtec causes less drowsiness and anticholinergic side effects like dry mouth and eyes. However, for those aiming to leverage sedative effects, such as for facilitating sleep, Benadryl remains an option.

By understanding key differences in safety, side effects, efficacy, and duration between these over-the-counter antihistamines, patients can make informed decisions with their doctors about the best allergy medication choice aligning with their needs.

FAQs on Benadryl and Zyrtec

Can I take Benadryl and Zyrtec together?

It's usually not recommended to take Benadryl and Zyrtec together. Both antihistamines can enhance drowsiness, and cause increased sedation when combined. Always consult your doctor before taking them together.

Can I take Benadryl or Zyrtec when pregnant?

Before taking any antihistamine like Benadryl or Zyrtec during pregnancy, you should check with your doctor. Zyrtec might be classified as safer during pregnancy compared to Benadryl by some doctors.

Can I take Zyrtec every day?

Yes, for most people, Zyrtec is considered safe for everyday use. When taken regularly at recommended doses, it does not usually cause significant sedation or anticholinergic side effects.

Can I take Benadryl every day?

Benadryl may cause more pronounced sedation and anticholinergic effects with regular, daily use at higher doses. It’s not typically advised to take Benadryl regularly for more than a few days without consulting your doctor.

How long do the effects of Benadryl and Zyrtec last in the body?

Benadryl stays in the body for 4 to 6 hours. Zyrtec lasts for a full 24 hours from the time you take it. This long-lasting effect makes once-daily use of Zyrtec convenient for treating allergy symptoms.

Illustration of a healthcare provider asking questions on a smart phone.
Allergy treatment - Online visit
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Illustration of a healthcare provider asking questions on a smart phone.
  • $29 one-time assessment
  • No video call or appointment necessary
  • Personalized treatment plan prescribed for your condition