Which Allergy Medicine Is Actually Most Effective?

a man with flu is walking in public park and sneezing in paper tissues
What's the Difference Between Zyrtec vs. Claritin?ProfessionalStudioImages - Getty Images

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If you've got seasonal allergies, it can feel like each year is worse than the one before. You're not crazy: Research shows that pollen seasons now start earlier, last longer and are more sneeze-and-itch provoking than they were in the past. That's thanks to climate change, as warm weather lasting longer gives more time for the offending plants to do their thing.

Cue you, cruising the aisles of your local drugstore to try to find a medication that will help you get through the itching, sneezing and other seasonal allergy symptoms you’re dealing with. Two of the biggies are Zyrtec and Claritin — over-the-counter drugs have been helping folks with seasonal allergies for years. But which is right for you?

And it matters, because although Zyrtec (the brand name for cetirizine) and Claritin (loratadine) are similar medications, “patients can absolutely have differing responses to Zyrtec and Claritin,” says Jamie Alan, PhD, an associate professor of pharmacology and toxicology at Michigan State University.


Zyrtec is a brand name for the drug cetirizine. “This is a second-generation antihistamine, which is less sedating than the first-generation antihistamines like Benadryl,” says Shaan Waqar, MD, an allergist and immunologist with ENT and Allergy Associates in Plainview, NY.

a white container with a green lid
a white container with a green lid

The long-acting, over-the-counter medication lasts up to 24 hours per dose, according to the Food and Drug Administration (FDA). It reaches peak concentration in your body an hour after you take it, and is used to treat allergy symptoms, including runny nose, nasal congestion, itchiness and hives.

Much of the research on the effectiveness of Zyrtec is older, but a 2014 randomized, double-blind, placebo-controlled study of more than 320 allergy sufferers found that those who took 10 milligrams of cetirizine a day for four weeks had “significantly greater overall improvement” in their allergy symptoms compared to people who took a placebo.

How Zyrtec works

Zyrtec works by blocking the histamine 1 receptor in your body, explains David Corry, MD, professor of allergy medicine at Baylor College of Medicine in Houston. “Histamine is a chemical that is released by a type of infection-fighting cells in the body called mast cells, but other cells can also release histamine,” he explains. “Once released, histamine acts on the histamine 1 receptor to cause the classic symptoms of allergy including itchy, watery eyes, runny nose, sneezing, and often cough.” By blocking this receptor, an antihistamine like Zyrtec tamps down the classic allergy symptoms in the process, these symptoms, says Dr. Corry.

Adults and children aged six and up should take one 10 milligram tablet of Zyrtec a day, according to the company that makes the drug. The effects of the medication usually kick in as fast as 20 minutes, research shows, and up to an hour after you take it.

Zyrtec cost

Zyrtec is widely available at drugstores and online, although there is a range of prices, depending on where you buy it. A 60-pack of 10 milligram tablets is currently $26 at Amazon, and $36 at Walgreens. You can also find it for $33 at Target.

Side effects of Zyrtec

  • Zyrtec is a widely available medication that can work quickly. “In the average patient, Zyrtec works at its maximum effect slightly faster — about 45 minutes —compared to Claritin (2 hours),” says Christopher Brooks, MD, an allergist and immunologist at The Ohio State University Wexner Medical Center. “However, for most patients who are taking it to prevent symptoms later in the day, this difference doesn’t matter too much.”

  • Like all medications, Zyrtec comes with a risk of side effects. “Zyrtec can cause drowsiness,” Dr. Brooks says. “While not as frequent as for older antihistamines like Benadryl, I still see drowsiness with Zyrtec quite a bit. In fact, pilots are not allowed to take Zyrtec before flying.” Dr. Brooks says he’s also seen eye and mouth dryness with patients who have taken Zyrtec, along with constipation, “especially at higher doses, which are used for chronic hives.”

  • Drug interactions aren’t common with Zyrtec, according to the FDA, Dr. Brooks says you’ll want to be careful about using other medications that can cause drowsiness at the same time.


Claritin is a brand name for loratadine. Like Zyrtec, this is a second-generation antihistamine. “The second generation drugs do not pass as readily into the brain and are less sedating,” Dr. Alan says.

claritin d allergy and congestion medicine
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Loratadine is also used to treat symptoms of allergies, like runny nose, congestion, and itchiness.

How Claritin works

Claritin works similarly to Zyrtec, Dr. Alan says, meaning it helps block the effects of symptom-inducing histamine on the body. It’s recommended that adults and children aged six and up take a 10 milligram tablet once a day or two five-milligram tablets twice daily to relieve symptoms of allergies.

But there are some differences between Claritin and Zyrtec: Claritin doesn’t cross the blood-brain barrier, so it’s unlikely to make you drowsy, she says. It also takes a bit longer to kick in, research shows: The effects of Claritin can be felt anywhere from one to three hours after you take it, reaching peak concentration in your body between eight and 12 hours after you take it.

But it does work for many people. A 2018 randomized, double-blind study on loratadine found that people who took the medication two hours after being exposed to ragweed pollen had “significant and durable improvement” in their symptoms compared to those who took a placebo.

How much is Claritin?

Like Zyrtec, the cost of Claritin varies depending on where you buy it. A 70-tablet pack of Claritin costs $22 at Amazon, and $48 at Walgreens. You can also find it for $42 at Target.

Side effects of Claritin

  • Drug interactions are not usually a problem. “Claritin drug interactions are also uncommon,” Dr. Brooks says. “It is mostly older antihistamines, such as Benadryl and hydroxyzine, where drug interactions occur.”

  • It is also less likely to make you drowsy, but it may, and there may be other side effects, at least for a small group. “Drowsiness is not as common with Claritin, but I still have some patients who experience drowsiness,” Dr. Brooks says. “Some patients report dry eyes and mouth, as well as constipation too, but most people do not have these sides effects.” People who have these side effects tend to be the ones who take the medication at high doses, he says. (Other side effects can include headache, nosebleed, sore throat, stomach pain, and diarrhea, according to Medline Plus.)

Bottom line: Which is more effective — Claritin or Zyrtec?

The answer is highly individual, and you may need to do some trial and error. “It really depends on the person,” Dr. Brooks says. “I often recommend a patient start with one, and if one doesn’t help them within two weeks they should try the other,” he says, adding that one is not objectively superior to the other.

And if nasal congestion is your main symptom of seasonal allergies, the answer may be neither, says Priya Patel, MD, assistant professor of clinical medicine in pulmonary, allergy, and critical care at Penn Medicine. “While antihistamines [like Zyrtec and Claritin] can help with sneezing, itching and runny nose, first line therapy for relief of nasal congestion includes a steroid or antihistamine nose spray.”

For most people, Dr. Corry recommends starting with Zyrtec, and then if that doesn't work, giving Claritin a go. “Cetirizine may be slightly more effective than loratadine,” he says. If you're older, though, Dr. Brooks recommends Claritin for you, because it's less likely to make you dizzy and risk your falling.

Ultimately, the right medication for you comes down to personal preference. “The two drugs are very similar, but some persons, after trying both, believe that one performs better than the other or, conversely, one produces fewer side effects than the other,” Dr. Corry says. “Personal preference is the usual deciding factor here.”

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