Should I Take Claritin, Zyrtec, or Allegra?

It's common for people with hives (urticaria) or hay fever (allergic rhinitis) to wonder which over-the-counter antihistamine they should take: Claritin (loratadine), Zyrtec (cetirizine), or Allegra (fexofenadine). All of these antihistamines have been available OTC without a prescription for a number of years.

But if you're thinking these antihistamines are the same, they're actually not. Depending on the allergic condition being treated, the age of the person, as well as other underlying issues (such as pregnancy), the best choice of antihistamine might be different.

Comparing Antihistamines

Verywell / Brianna Gilmartin

How Antihistamines Work

When you've been exposed to a substance you're allergic to (such as pet dander, dust mite, ragweed, or peanuts), your body produces histamine, which is a chemical messenger released by cells in the immune system to alert and activate other cells and proteins of the immune system.

Histamine causes the typical allergy symptoms of sneezing, stuffy and runny nose, watery and itchy eyes, and an itchy throat that you associate with exposure to whichever allergens you are sensitive to.

Antihistamines reduce the amount of histamine circulating in your system, thereby reducing symptoms.

Comparing Claritin, Zyrtec, and Allegra

Claritin, Zyrtec, and Allegra are all considered newer generation antihistamines. First-generation antihistamines, such as Benadryl (diphenhydramine) and Atarax (hydroxyzine), can be helpful for allergies and hives as well, but their use is limited due to side effects such as fatigue and sedation (sleepiness).

So while Claritin, Zyrtec, and Allegra are all newer generation antihistamines that can treat hay fever or hives, there may be some advantages for each of these over the others.

Pregnancy and Lactation

Claritin and Zyrtec have been shown to have a good safety profile in studies of pregnant animals, but there are no human studies available. During pregnancy, they are preferred over Allegra, which has shown adverse fetal effects in animal studies.

Allegra is considered to be safer for breastfeeding mothers compared to Zyrtec and Claritin. However, all three are deemed to be safe during lactation.

Side Effects

All three antihistamines may cause side effects such as:

  • Blurred vision
  • Confusion
  • Dry mouth
  • Drowsiness
  • Dizziness
  • Nausea and vomiting
  • Mood changes (mostly limited to some children)
  • Difficulty urinating 

That said, the side effect profile may vary slightly among them. For instance, Allegra is completely non-sedating (doesn't make people sleepy), while Claritin is minimally sedating (makes only a small number of people sleepy). Zyrtec, on the other hand, causes sedation in approximately one in six people who take the medication. 


While you should consult your healthcare provider about the best way to take any medication, there are widely accepted dosing recommendations for all three of these antihistamines. First and foremost, each works best when taken daily rather than intermittently. 

All of these antihistamines are indicated for adults and children 2 years of age and older, with Zyrtec and Claritin dosed once a day for all ages.

Allegra is dosed twice a day for children age 2 to 11, and once a day for adults and children age 12 years and older. Finally, since Allegra can be used in children as young as 6 months of age, it's sometimes the ideal choice for young children.

Effectiveness and Speed of Relief

Besides dosing, there are some slight differences in how quickly or well the drugs work. For example, while Claritin is effective for treating hay fever and hives, other antihistamines, such as Zyrtec and Allegra, work better and faster and last longer.

Zyrtec and Allegra work quickly for the treatment of allergic rhinitis and hives, typically within less than an hour. On the other hand, studies show that Claritin takes many hours to start working.

Studies show that Allegra is nearly as good as Zyrtec at treating hayfever. However, Zyrtec and its isomer Xyzal (levocetirizine) appear to be better medicines for the treatment of hives.

There are also some unexpected nuances associated with each of the antihistamines. For example, if you're taking Allegra, it's important to avoid drinking fruit juice for one to two hours before you take the medication and one to two hours after. Juices such as orange juice or grapefruit juice can decrease the absorption of Allegra by nearly half.

Talking With Your Healthcare Provider

The best antihistamine choice for any one person is based on the degree of symptom relief desired and the degree of side effects you're willing to tolerate.

For mild to moderate allergy symptoms, Allegra may be preferable to drugs such as Zyrtec since these other drugs are more sedating. Yet for severe symptoms that are interfering with work, school, or play, a medication such as Zyrtec may be needed.

Note that every person is different. This means that despite what studies say, there are many people who do not experience any fatigue on Zyrtec or Xyzal. Likewise, there are people who do experience fatigue on Allegra.

It's sometimes helpful to try different medications to see which works best for you as an individual. If you try this, though, talk with your healthcare provider first.

You might keep a journal to get an objective measure of which drug works best. For instance, you can write down your most annoying symptoms, and rank them from 1 to 10 based on how well they are controlled by different medications.

Talk with an allergist about the possibility of allergy testing and allergy shots. While allergy shots require more follow-up (and more pokes) they can sometimes cure allergies (or at least significantly reduce their symptoms) so that medications are no longer needed. In addition, it's thought that allergy shots may sometimes help prevent the development of new allergies.

Frequently Asked Questions

Why do some allergy medicines make you sleepy? 

First-generation antihistamines cross the blood-brain barrier, which can produce a sedative effect. However, not everyone feels sleepy when taking these. Meanwhile, some people feel drowsy taking the second-generation antihistamines, which don’t cross the blood-brain barrier.

Which over-the-counter antihistamine is the strongest?

Among second-generation antihistamines, the most potent are Xzal (levocetirizine) and Allegra (fexofenadine), which are available over the counter.

A Word From Verywell

In the end, Claritin, Zyrtec, and Allegra are all good antihistamine options and are generally well-tolerated. But there are some differences between them, as outlined above, which may make one of these antihistamines better than the others depending on a person's needs and characteristics. 

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4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. So M, Bozzo P, Inoue M, Einarson A. Safety of antihistamines during pregnancy and lactationCan Fam Physician. 2010;56(5):427-429.

  3. Cleveland Clinic. Antihistamines. July 13, 2020.

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