Should I Take Allegra, Claritin, or Zyrtec?

Learn about the best choices for allergy relief

Allegra (fexofenadine), Claritin (loratadine), or Zyrtec (cetirizine) are over-the-counter (OTC) antihistamines used to treat allergies. Second-generation antihistamines relieve allergy symptoms like congestion, hives (urticaria), and itching without drowsiness.

Allegra, Claritin, and Zyrtec are used to treat common allergies like pollens, pet dander, or dust mites. The drugs may seem interchangeable, but there are some differences that may make one the better choice for you.

This article compares Allegra, Claritin, and Zyrtec. It explains their similarities and differences, how quickly each antihistamine begins to work, and potential side effects. In addition, it details which allergy medications are safe to use in pregnancy.

Comparing Antihistamines

Verywell / Brianna Gilmartin

Allegra vs. Zyrtec vs. Claritin

Claritin, Zyrtec, and Allegra are all considered newer-generation antihistamines. Antihistamines work by blocking histamines and calming your allergic response.

Exposure to an allergen such as pet dander, dust mites, pollen, or peanuts prompts the immune system to release chemicals called histamines. Histamines cause allergy symptoms like congestion, runny nose, watery and itchy eyes, and an itchy throat.

First-generation antihistamines, such as Benadryl (diphenhydramine) and Atarax (hydroxyzine), can also be helpful for allergies and hives, but their use is limited because of side effects such as fatigue and sedation (sleepiness). Newer antihistamines are less likely to make you tired.

Pregnancy and Lactation

Claritin and Zyrtec have been shown to have a good safety profile in studies of pregnant animals, but there are no studies on human expecting mothers. Still, during pregnancy, these drugs 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 considered safe during lactation.

Side Effects

All three antihistamines may cause side effects such as:

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

This said, the side effect profile may vary slightly. For instance:

  • Allegra is completely non-sedating (doesn't make people sleepy)
  • Claritin is minimally sedating (makes only a small number of people sleepy)
  • Zyrtec causes sedation in about one in six people who take it

Dosage

You should consult your healthcare provider about the best way to take any medication, but there are standard dosing recommendations for all three of these antihistamines. Each of these medications works best when taken daily rather than occasionally. 

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

Allegra is dosed twice a day for children from age 2 to 11 and once a day for adults and children ages 12 and older. Since Allegra can be used in children as young as 6 months old, 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 how well the drugs work. Zyrtec and Allegra work quickly for the treatment of allergic rhinitis and hives, typically within less than an hour. By contrast, studies show that Claritin takes many hours to start working.

Studies also show that Allegra and Zyrtec are good at treating hay fever and hives. However, Zyrtec appears to be a better medicine for the treatment of hives.

Heed Allegra's "No-Juice" Zone

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 afterwards. Juices such as orange juice or grapefruit juice can decrease the absorption of Allegra by nearly half.

Deciding Which One Is Best for You

For mild to moderate allergy symptoms, Allegra may be preferable since the 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. It all depends on how much symptom relief you need and the degree of side effects you can tolerate.

Note that people may react differently to these drugs. For example, many people do not experience any fatigue on Zyrtec. Likewise, some people do experience fatigue on Allegra.

Always Read Drug Labels

Antihistamines are safe when they're used as directed. They can be dangerous when used improperly or carelessly. For example, some antihistamines contain pain medication. So taking another pain remedy in addition to the antihistamine could cause an overdose.

Summary

Claritin, Zyrtec, and Allegra are all good antihistamine options and are generally well-tolerated by many people. But there are some differences between them that may make one of these antihistamines better for you than the others.

For example, Zyrtec and Allegra may work faster than Claritin. Zyrtec and Claritin can make you sleepy, while Allegra won't. And Zyrtec and Claritin, but not Allegra, are recommended for use in pregnant women. If you're unsure of which antihistamine to select, consult your healthcare provider or pharmacist.

A Word From Verywell

If you find that you cannot get symptom relief from any OTC allergy medication, consider seeing an allergist—someone who specializes in diagnosing and treating allergies. They can determine the next steps, which may include allergy shots.

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. Second-generation antihistamines don't cross this barrier, so they are less likely to make you feel drowsy.

  • Which over-the-counter antihistamine is the strongest?

    Allegra (fexofenadine) is the most potent of the second-generation OTC antihistamines.

  • Can you take Allegra and Benadryl together?

    No. According to the National Capital Poison Center, this can cause serious side effects.

  • Can you take Allegra and Claritin together?

    No. It is not safe to take any two antihistamines at the same time.

  • How long does it take for Allegra to work?

    Allegra usually starts to work within an hour. 

  • How long does it take for other allergy medicines to work?

    You can expect an allergy medication to start taking effect within one to several hours. Check the product packaging for details.

  • Does Zyrtec raise blood pressure?

    No, Zyrtec does not raise blood pressure. However, Zyrtec-D also contains pseudoephedrine, which can. If you have high blood pressure, avoid allergy medications that are labeled as D (for decongestant) unless otherwise recommended by your healthcare provider.

  • Does Allegra, Claritin, or Zyrtec clear up mucus?

    Antihistamines can help clear up mucus but aren't always enough on their own. Heavy congestion often requires a decongestant to resolve. Allegra-D, Claritin-D, and Zyrtec-D also contain the decongestant pseudoephedrine. D formulations typically last 12 hours instead of 24 hours.

7 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.
  1. National Library of Medicine. MedlinePlus. Histamine: The stuff allergies are made of.

  2. Kar S, Krishnan A, Preetha K, Mohankar A. A review of antihistamines used during pregnancy. J Pharmacol Pharmacother. 2012;3(2):105-8. doi:10.4103/0976-500X.95503.

  3. Servey J, Chang J. Over-the-counter medications in pregnancy. Am Fam Physician. 2014 Oct 15;90(8):548-55.

  4. So M, Bozzo P, Inoue M, Einarson A. Safety of antihistamines during pregnancy and lactationCan Fam Physician. 2010;56(5):427-429.

  5. National Capital Poison Center. Safe use of antihistamines.

  6. American Academy of Allergy Asthma & Immunology. Antihistamines: If/when are first generation medications advantageous over newer antihistamines?

  7. Church DS, Church MK. Pharmacology of antihistamines. World Allergy Organization Journal. 2011;4(3):S22-S27. doi:10.1097/WOX.0b013e3181f385d9.

Additional Reading

By Daniel More, MD
Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and currently practices at Central Coast Allergy and Asthma in Salinas, California.