Should I Take Allegra, Claritin, or Zyrtec?

If you have allergies to pollens, pet dander, or dust mites, or are prone to hives (urticaria), you may have taken an over-the-counter (OTC) antihistamine such as Allegra (fexofenadine), Claritin (loratadine), or Zyrtec (cetirizine) to relieve your symptoms.

These three common allergy medications yield similar results, so they may seem interchangeable. However, there are differences that may make one a better choice for you than the others.

This article compares Allegra, Claritin, and Zyrtec to help you decide which one to reach for at the pharmacy.

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 mites, pollen, or peanuts), your body perceives it as a threat to your immune system. In response, cells release chemicals called histamines.

Histamines are important components of the immune system, but in people with allergies, they go into overdrive trying to eliminate the allergen. This is what causes symptoms such as a stuffy and runny nose, watery and itchy eyes, and an itchy throat.

Antihistamines work by blocking histamines and calming your allergic response.

Antihistamines Blunt Histamines

Antihistamines reduce allergy symptoms by lowering the amount of a chemical your body releases in an effort to get rid of the offending allergen.

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 also be helpful for allergies and hives, but their use is limited because of side effects such as fatigue and sedation (sleepiness).

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 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. But check the product packaging for details.

Was this page helpful?
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