What Does the Drug Cetirizine Do For You? A Comprehensive Guide

October 7, 2025 •

3 min read

In 2023, cetirizine was the 55th most commonly prescribed medication in the United States, with over 11 million prescriptions. So, what does the drug cetirizine do for you? It is a potent second-generation antihistamine used to relieve allergy symptoms like sneezing, itching, watery eyes, and hives.

Quick Summary

Cetirizine is an over-the-counter antihistamine that blocks histamine's effects, relieving symptoms of allergies and hives. It is known for its fast action and 24-hour relief, with less drowsiness than older allergy drugs.

Key Points

What it is: Cetirizine is a second-generation antihistamine medication used to treat allergy symptoms like sneezing, itching, and hives.
How it works: It functions by blocking the action of histamine, a substance the body releases during an allergic reaction.
Primary Uses: It is approved for treating seasonal and perennial allergic rhinitis (hay fever) and chronic idiopathic urticaria (hives).
Speed and Duration: Cetirizine works quickly, with effects often felt within an hour, and one dose typically lasts for 24 hours.
Drowsiness: While considered 'non-drowsy,' it is more likely to cause sleepiness compared to other second-generation antihistamines like loratadine or fexofenadine.
Dosage Forms: It is available over-the-counter in tablets, chewable tablets, and liquid syrup for adults and children.
Important Warning: The FDA has warned of a rare risk of severe itching after stopping long-term daily use of cetirizine.

Understanding Cetirizine and Its Role in Allergy Relief

Cetirizine, also known as Zyrtec, is a second-generation antihistamine widely used to manage allergy symptoms. It is effective for conditions such as hay fever (allergic rhinitis), allergic conjunctivitis, and chronic urticaria (hives). Approved by the FDA for over-the-counter use in 2007, cetirizine helps alleviate itching, sneezing, runny nose, and watery eyes. A key advantage over first-generation antihistamines like diphenhydramine (Benadryl) is its lower tendency to cause drowsiness due to less penetration of the blood-brain barrier.

How Cetirizine Works: The Mechanism of Action

Allergic reactions involve the release of histamine by the body in response to allergens. Histamine binds to H1 receptors, leading to typical allergy symptoms like itching, swelling, sneezing, and increased mucus.

Cetirizine acts by blocking these peripheral H1 receptors, preventing histamine from binding and thus relieving allergic symptoms. Its effects are usually noticeable within 20 to 60 minutes and last for about 24 hours, allowing for once-daily use. Some research also suggests cetirizine has anti-inflammatory effects that contribute to managing the allergic response.

Conditions Treated with Cetirizine

Cetirizine is effective for treating various allergic conditions:

Seasonal and Perennial Allergic Rhinitis: It helps reduce sneezing, runny nose, and itching caused by allergens like pollen, dust mites, and pet dander.
Chronic Urticaria (Hives): It is a primary treatment for chronic hives, reducing their severity and associated itching.
Allergic Conjunctivitis: An eye drop version of cetirizine is available for treating itchy, red, and watery eyes due to allergies.
Other Allergic Reactions: It can also be used for itching and redness from other mild skin allergies.
Off-Label Uses: Healthcare providers may use it off-label as an additional treatment for anaphylaxis (after epinephrine) or to prevent reactions to other medications.

Dosage and Administration

Cetirizine comes in tablets, chewable tablets, orally disintegrating tablets, and liquid syrup. The appropriate amount to take can vary based on individual factors such as age and symptom severity. It is important to follow the specific instructions provided on the product packaging or by a healthcare professional. Those with kidney or liver issues should consult a doctor regarding appropriate use. Cetirizine can be taken with or without food.

Comparison with Other Antihistamines

Here is a comparison of cetirizine with other common antihistamines:


Feature	Cetirizine (Zyrtec)	Loratadine (Claritin)	Fexofenadine (Allegra)	Diphenhydramine (Benadryl)
Generation	2nd Generation	2nd Generation	2nd Generation	1st Generation
Onset of Action	Fast (approx. 1 hour)	Slower (up to 3 hours)	Fast (approx. 2 hours)	Fast (approx. 30-60 mins)
Drowsiness	Low to moderate risk	Lower risk	Least likely to cause drowsiness	High risk of drowsiness
Duration	~24 hours	~24 hours	~24 hours	4-6 hours

Potential Side Effects and Warnings

While generally safe, cetirizine can cause side effects. Common ones include:

Drowsiness
Tiredness
Dry mouth
Headache
Sore throat or cough

Cetirizine is often called "non-drowsy," but it can cause more sleepiness than loratadine or fexofenadine. Combining cetirizine with alcohol or other central nervous system depressants can increase drowsiness. The FDA issued a warning on May 16, 2025, about a rare possibility of severe itching upon stopping long-term use of oral cetirizine.

Conclusion

Cetirizine provides rapid and effective 24-hour relief from various allergy symptoms by blocking histamine. As a second-generation antihistamine, it generally causes less drowsiness than older medications, making it a good option for managing hay fever, hives, and other allergies. Although available over-the-counter, consulting a healthcare provider is recommended, especially if you have existing health conditions or are taking other medications.

For more information from an authoritative source, you can visit Cetirizine: MedlinePlus Drug Information.

Frequently Asked Questions

Cetirizine typically starts to work within 20 to 60 minutes after taking it, with its effects lasting for about 24 hours.

Yes, second-generation antihistamines like cetirizine are generally considered safe for daily, long-term use, especially for managing chronic allergies. However, there is a rare risk of severe itching after stopping long-term treatment, so it's best to consult a doctor before stopping.

The most common side effect of cetirizine is drowsiness or sleepiness, although it is less sedating than older, first-generation antihistamines.

It is best to avoid drinking alcohol while taking cetirizine, as alcohol can increase the drowsiness caused by the medication.

Both are second-generation antihistamines. However, cetirizine tends to work faster (within about an hour) compared to loratadine (up to three hours), but cetirizine also has a slightly higher chance of causing drowsiness.

If you miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed one and continue with your regular schedule. Do not take a double dose to make up for it.

You should not take cetirizine if you are allergic to it or to hydroxyzine. People with kidney or liver disease should consult a doctor before use, as a lower amount may be needed.