Key takeaways
Zyrtec is an over-the-counter antihistamine that can help relieve allergy symptoms, such as sneezing, itchy eyes, watery eyes, runny or stuffy nose, hives, and sore throat
Zyrtec can cause drowsiness in some people, so take it at night instead of in the morning if drowsiness occurs.
If Zyrtec is not working or causing side effects, work with a healthcare provider to find the best treatment plan for you.
Zyrtec (cetirizine) is an over-the-counter (OTC) antihistamine approved by the FDA to treat seasonal allergies in those ages two years and older and year-round allergic rhinitis and chronic hives (urticaria) in those ages six months and older. It blocks histamine receptors, reducing symptoms such as sneezing, itchy eyes, watery eyes, runny or stuffy nose, hives, and sore throat. Zyrtec is less sedating than first-generation antihistamines, such as diphenhydramine, but it can still cause drowsiness. If Zyrtec causes drowsiness, it is best to take it closer to bedtime instead of in the morning. However, it is appropriate to take it in the morning if drowsiness is not a side effect. As a once-daily dose, Zyrtec’s effects should last for 24 hours, so the best time of day is what works best for each individual patient.
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Is it better to take Zyrtec at night or in the morning?
There’s no set time of day that’s best for taking Zyrtec. According to astudy in Allergy & Rhinology, cetirizine provides 24-hour allergy relief regardless of when you take it. It also starts to work within 30 to 60 minutes.
Ultimately, the answer comes down to what works best for each individual. “This will be on patient preference,” says Dr. Kanwar Kelley, MD, JD, a board-certified otolaryngologist (ENT) and founder of Side Health. “The medication will affect everyone differently, so it is better to consider when you are more likely to experience symptoms.”
One question that might arise is whether taking Zyrtec at night can improve sleep quality by reducing allergy symptoms. Dr. Raj Dasgupta, MD, a quadruple board-certified physician and director of the Internal Medicine residency program at Huntington Memorial Hospital, speaks to how a night dose can indirectly improve sleep quality (if allergies keep you up) by reducing symptoms like nasal congestion, sneezing, and itching.
However, taking Zyrtec at night isn’t necessarily the more popular choice. “Most people take Zyrtec in the morning, which can address allergy symptoms without causing drowsiness,” Dr. Dasgupta says. “Some people may still experience mild drowsiness, so it’s important to see how your body responds.”
Should you take Zyrtec at night if it makes you sleepy?
If some people prefer taking Zyrtec at night and others prefer morning, is there a “best” time? “The best time to take Zyrtec depends on your daily routine,” Dr. Dasgupta says. While that factor is flexible, he urges taking it around the same time every day.
What happens if you miss a dose of Zyrtec?
If you miss a dose of Zyrtec, you can take it as soon as you remember, as long as it’s not closer to the next dose. However, you should only take one day’s worth; don’t take two doses in one day.
Other ways to manage allergy symptoms
First and foremost, knowing what you’re allergic to is crucial. If you’re not sure, or even if you know some triggers, but possibly not others, consider allergy testing with a medical professional. They can inform you how to alleviate or reduce your symptoms, which could possibly involve taking a medication like Zyrtec.
Common side effects of Zyrtec include allergy symptoms: headache, sore throat, dry mouth, and cough. Side effects that are less common and more severe include low blood pressure, airway closure, dizziness, a fast heartbeat, a weak pulse, and fainting. It is also possible to experience an allergic reaction to Zyrtec, and it should be stopped immediately if that happens. That’s where other treatment options come in.
Besides Zyrtec, other allergy treatments and OTC medications include other antihistamines, decongestants, allergy immunotherapy (allergy shots), saline spray, and intranasal corticosteroids, such as Flonase. Additionally, air purifiers and frequent cleaning of an environment can help alleviate some allergies.
“You can also reduce allergens around your home by keeping windows closed, using air purifiers, or minimizing outdoor exposure during peak allergy season,” Dr. Dasgupta says. “Tailoring your approach based on your schedule and symptoms will help you find the most effective treatment.”
Again, don’t forget the importance of not doing this alone; consult with a healthcare provider when determining an appropriate allergy plan. They can assess what would be most helpful for each person specifically.
Zyrtec and other allergy medications can be purchased at a lower price by using a SingleCare prescription discount card.
RELATED: Can I use a prescription savings card for OTC medications?
When to talk to a healthcare provider
Mild allergies can usually be treated at home with OTC medications. Community pharmacists are a great resource when shopping for an OTC treatment. However, if at-home treatments are not working or allergies are getting worse, it is best to consult a healthcare provider that can further examine you and prescribe medications if needed. They can work with you to find the best treatment plan. When speaking to them, it is important to provide them with an accurate medical history and medication list, both prescription and OTC.
Frequently asked questions
How long does Zyrtec last?
Zyrtec’s effects last for at least 24 hours for most people. It may also last longer in those with reduced kidney function.
How long does Zyrtec take to work?
Zyrtec takes about 30 to 60 minutes to work. The time to effectiveness may be delayed to about 90 minutes if taken with food.
Should you take Zyrtec before allergy symptoms start?
Zyrtec can be taken before allergy symptoms start in order to prevent them, but it can also be taken as needed after symptoms have occurred. Some people take Zyrtec if they anticipate that they will be around somewhere that triggers their allergies, such as visiting a friend with a pet or taking a walk outside during allergy season.
The SingleCare prices in this article are the most accurate at the time of publishing in ZIP code 23666 as of Oct. 6, 2026. Prices vary by pharmacy. Visit our coupon page for updated drug prices at pharmacies near you.
- FDA requires warning about rare but severe itching after stopping long-term use of oral allergy medicines cetirizine or levocetirizine (Zyrtec, Xyzal, and other trade names), U.S. Food & Drug Administration (2026)
- Assessment of different cetirizine dosing strategies on seasonal allergic rhinitis symptoms: Findings of two randomized trials, Allergy & Rhinology (2018)
- Cetirizine tablets, Cleveland Clinic
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