- Zyrtec and Benadryl are antihistamines designed to relieve allergy symptoms. Though they work similarly, they have distinct differences that make them unique.
- Zyrtec is better for long-term relief. It lasts up to 24 hours and causes less drowsiness, so it’s a good option for daily allergy management.
- Benadryl works faster but causes drowsiness. It relieves symptoms within 30 minutes but only lasts 4–6 hours.
Zyrtec and Benadryl are allergy medications that help relieve sneezing, itching, runny nose, and watery eyes. People use them for allergies caused by pollen, pet dander, and other allergens. But while both medications work, they are not the same.
This article will compare Zyrtec and Benadryl, including how they work and their side effects. By the end, you'll have a better understanding of which one might be a better choice for your allergy symptoms.
What are Zyrtec and Benadryl?
Zyrtec and Benadryl are both over-the-counter (OTC) antihistamines used to treat allergy symptoms. While they work in similar ways, they have key differences that set them apart.
Zyrtec
Zyrtec (cetirizine) relieves sneezing, runny nose, itchy eyes, and hives. It is a second-generation antihistamine, meaning it causes less drowsiness than older allergy medicines. People often take Zyrtec for seasonal allergies, pet allergies, and chronic hives [*].
It is available in various forms, including tablets, chewable tablets, and liquid syrup.
Benadryl
Benadryl (diphenhydramine) also treats allergy symptoms like sneezing, runny nose, and itching. However, it is a first-generation antihistamine, meaning it crosses into the brain more easily and is more likely to cause drowsiness. Because of this, it is often used as a nighttime allergy medicine or sleep aid [*].
Benadryl comes in forms such as tablets, liquid gels, chewable tablets, and liquid syrup.
How Do Zyrtec and Benadryl Work?
Both Zyrtec and Benadryl work by blocking histamine, a chemical in the body that causes allergy symptoms. However, they do this in slightly different ways, which affects how long they last and whether they cause drowsiness.
Zyrtec Mechanism of Action
Zyrtec mainly works on histamine receptors outside the brain, so it relieves allergy symptoms without making you too sleepy. It starts working within an hour and lasts up to 24 hours, making it a good choice for all-day allergy relief.
In addition to blocking histamine, Zyrtec also helps reduce inflammation. It does this by preventing certain immune cells, like neutrophils and eosinophils, from reaching areas where they can cause swelling and irritation. This can help with symptoms like a stuffy nose and itching.
Benadryl Mechanism of Action
Benadryl blocks histamine in both the body and the brain by targeting the H1 receptor, which helps relieve allergy symptoms like sneezing and itching. However, because it also affects the brain, it can cause drowsiness. Benadryl works fast, often within 30 minutes, but only lasts about 4 to 6 hours, so it needs to be taken multiple times.
What Allergy Symptoms Do Zyrtec and Zyrtec Relieve?
Both Zyrtec and Benadryl help with common allergy symptoms. However, they are used in slightly different situations.
Zyrtec is often taken for long-term allergies, such as seasonal allergies and pet allergies. It helps relieve sneezing, a runny or stuffy nose, itchy, watery eyes, and hives or skin itching. Since it lasts for 24 hours and causes less drowsiness, many people use it for daily allergy management.
Benadryl works well for quick relief of allergy symptoms and is often used for short-term issues, such as allergic reactions or trouble sleeping. It helps with sneezing, a runny nose, itchy, watery eyes, and hives or swelling from allergic reactions. It can also relieve itching from bug bites or rashes. However, because Benadryl can cause drowsiness, it is more commonly used at night or when fast relief is needed.
What are the Recommended Dosages for Benadryl and Claritin?
For Benadryl, adults and children 12 years and older can take 25–50 mg every 4 to 6 hours as needed. Children 6 to 11 years old can take 12.5–25 mg every 4 to 6 hours. It should not be given to children under 6 unless a doctor says it’s okay.
For Claritin, adults and children 6 years and older can take 10 mg once a day. Children 2 to 5 years old can take 5 mg once a day. Always check with a doctor before giving Claritin to kids under 2.
What are the Side Effects of Zyrtec and Benadryl?
Like all medications, Zyrtec and Benadryl can cause side effects. While both treat allergies, their side effects are different, especially when it comes to drowsiness.
Zyrtec Side Effects
Common side effects of Zyrtec include drowsiness, dry mouth, dizziness, and headache. Some people may also experience stomach pain or nausea, but these are less common. Since Zyrtec is a second-generation antihistamine, it usually causes less drowsiness than Benadryl.
Benadryl Side Effects
Benadryl is more likely to cause drowsiness, dizziness, dry mouth, and blurred vision. Some people may also feel confused, have trouble urinating, or experience constipation. Because it makes you sleepy, Benadryl is not the best choice for daytime use if you need to stay alert.
How Long Does It Take for Zyrtec and Benadryl to Start Working?
Zyrtec starts working within 1 hour after taking it. Benadryl works faster, usually within 30 minutes, which makes it a good option for immediate symptom relief.
How Long Do the Effects of Zyrtec and Benadryl Last?
Zyrtec provides relief for up to 24 hours, so it only needs to be taken once a day. In contrast, Benadryl lasts 4 to 6 hours, meaning it may need to be taken multiple times throughout the day for continued relief.
Which Drugs Shouldn’t Be Taken With Zyrtec or Benadryl?
Certain medications can interact with Zyrtec and Benadryl, which would increase the risk of side effects.
Avoid taking Zyrtec with other antihistamines, sedatives, or alcohol, as this can cause drowsiness. It may also interact with some anxiety medications and muscle relaxants.
Avoid taking Benadryl with other sedating medications, such as sleeping pills, opioid pain relievers, or anti-anxiety drugs. Combining Benadryl with alcohol or muscle relaxants can also increase drowsiness and dizziness.
If you take other medications, consult your doctor or pharmacist before using Zyrtec or Benadryl.
Warnings and Precautions for Zyrtec and Benadryl
Although Zyrtec causes less drowsiness than Benadryl, it can still make some people feel tired. Avoid driving or operating heavy machinery until you know how it affects you. People with liver or kidney disease should consult a doctor before taking Zyrtec, as dosage adjustments may be needed.
Benadryl causes significant drowsiness and can impair coordination and alertness. It should not be taken before driving or performing tasks that require focus. Older adults are more sensitive to its effects and may experience confusion or dizziness. Benadryl should also be avoided if taking other sedating medications. Always check with a doctor before using Benadryl long-term.
Can You Take Zyrtec and Benadryl Together?
It is not recommended to take Zyrtec and Benadryl together. Both are antihistamines, and combining them can increase the risk of side effects like extreme drowsiness, dizziness, and dry mouth. Taking both may also lead to overdose symptoms.
If you need stronger allergy relief, consult a doctor for safer options. They can provide guidance on appropriate medications and dosages.
Frequently Asked Questions
Many people wonder which allergy medicine is best for them. Below are answers to common questions about Zyrtec and Benadryl to help you decide.
Which is better for allergies, Zyrtec or Benadryl?
Zyrtec is usually better for long-term allergy relief because it lasts 24 hours and causes less drowsiness. Benadryl works faster but is best for short-term use due to its sedating effects.
Which one lasts longer, Zyrtec or Benadryl?
Zyrtec works longer since it lasts up to 24 hours, while Benadryl only lasts 4 to 6 hours.
Which is safer for long-term use, Zyrtec or Benadryl?
Zyrtec is safer for long-term use because it has fewer side effects and does not cause as much drowsiness. Benadryl is not recommended for daily use, especially for older adults, due to its sedative effects.
Does Zyrtec or Benadryl work faster?
Benadryl works faster in about 30 minutes, while Zyrtec takes about an hour to take effect.
Is Zyrtec or Benadryl better for hives?
Both can help with hives, but Zyrtec is preferred for chronic hives because it provides longer-lasting relief with fewer side effects. Benadryl may be better for sudden, severe allergic reactions, but a doctor should be consulted.
Does Zyrtec make you drowsy like Benadryl?
Zyrtec can cause drowsiness in some people, but it is much less sedating than Benadryl.
The Bottom Line
Zyrtec and Benadryl are both effective for allergy relief, but they serve different purposes. Zyrtec is best for long-term allergy management because it lasts 24 hours and causes less drowsiness. Benadryl works faster but is better suited for short-term use due to its sedating effects.
If you're looking for an alternative, consider Allermi, a customizable nasal spray that combines up to four FDA-approved ingredients. Designed for daily use, Allermi provides targeted relief based on your specific allergy symptoms.
Always consult a doctor to find the best option for you.
References:
- Naqvi A, Patel P, Gerriets V. Cetirizine. [Updated 2024 May 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549776/
- Sicari V, Zabbo CP. Diphenhydramine. [Updated 2023 Jul 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526010/
