Should I take Claritin, Zyrtec or Allegra?


People with hives ( hives ) or hay fever ( allergic rhinitis ) often wonder which OTC antihistamine to take: Claritin (Loratadine), Zyrtec (Cetirizine), or Allegra (Fexofenadine). All of these antihistamines have been available without a prescription for several years.

But if you think these antihistamines are the same, in fact they are not. Depending on the allergic condition being treated, the person's age, and other underlying problems (such as pregnancy), the best antihistamine option may be different.

Get Medication Information / Brianna Gilmartin

How Antihistamines Work

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

Histamine causes typical allergy symptoms, such as sneezing, stuffy and runny nose, watery eyes, and itchy eyes and itchy throat, which is associated with exposure to any allergen you are sensitive to.

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

Comparison of Claritin, Zyrtek and Allegra

Claritin, Zyrtec, and Allegra are considered next-generation antihistamines. First-generation antihistamines like Benadryl (diphenhydramine) and Atarax ( hydroxyzine ) may also be helpful for allergies and hives, but their use is limited due to side effects such as fatigue and sedation (drowsiness) .

So while Claritin, Zyrtec, and Allegra are next-generation antihistamines that can treat hay fever or hives, each may have some benefits over the others.

Pregnancy and breastfeeding

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

Allegra is considered safer for breastfeeding mothers compared to Zyrtec and Claritin. However, all three are considered safe while breastfeeding.

Side effects

All three antihistamines can cause side effects such as:

  • Blurry vision
  • Confusion
  • Dry mouth
  • Drowsiness
  • Dizziness
  • Nausea and vomiting
  • Mood swings (mainly in some children)
  • Difficulty urinating

However, your side effect profile may vary slightly. For example, Allegra is not sedating (it does not cause drowsiness in people) and Claritin has minimal sedation (it only causes drowsiness in a small number of people). Zyrtec, on the other hand, causes sedation in about one in six people taking this drug.


While you should consult your doctor about the best way to take any medication, there are generally accepted dosage guidelines for all three antihistamines. First of all, each of them works best when taken daily rather than periodically.

All of these antihistamines are indicated for adults and children from 2 years of age, while Zyrtec and Claritin are prescribed once a day for all ages.

Allegra is prescribed twice a day for children 2 to 11 years old and once a day for adults and children 12 years and older. Finally, since Allegra can be used in children as young as 6 months of age, it is sometimes the perfect option for young children.

Efficiency and speed of assistance

Apart from the dose, there are small differences in the speed or effectiveness of the medications. For example, while Claritin is effective in treating hay fever and hives, other antihistamines like Zyrtec and Allegra work better, faster, and last longer.

Zyrtec and Allegra work quickly to treat allergic rhinitis and hives, usually in less than an hour. On the other hand, research shows that Claritin takes many hours to work.

Research shows that Allegra is almost as effective in treating hay fever as Zyrtec. However, Zyrtec and its isomer Xyzal (levocetirizine) appear to be the best medications for treating hives .

There are also some surprising nuances associated with each of the antihistamines. For example, if you are taking Allegra, it is important to avoid drinking fruit juice an hour or two before taking the medicine and an hour or two after. Juices like orange or grapefruit can cut allegra absorption by almost half.

Talk to your healthcare provider

The best antihistamine choice for anyone is based on the degree of symptom relief desired and the degree of side effects that you are willing to tolerate.

For mild to moderate allergy symptoms, Allegra may be preferred over medications like Zyrtec because these other medications are more sedating. However, for severe symptoms that interfere with work, school, or play, a medication such as Zyrtec may be needed.

Keep in mind that all people are different. This means that despite what the studies say, there are many people who do not experience fatigue when taking Zyrtec or Xyzal. Also, there are people who   do   I'm tired of Allegra.

Sometimes it helps to try different medications to see which one works best for you as an individual. If you try this, talk to your doctor first.

You can keep a journal to get an objective assessment of which medicine works best. For example, you can write down your worst symptoms and rank them from 1 to 10 based on how well various medications control them.

Talk to your allergist about allergy testing and allergy shots . Although allergy shots require more supervision (and more shots), they can sometimes cure the allergy (or at least significantly reduce its symptoms) so that medications are no longer needed. It is also believed that allergy shots can sometimes help prevent the development of new allergies.

Frequently asked questions

Why do certain allergy medications cause drowsiness?

First-generation antihistamines cross the blood-brain barrier , which can be sedating. However, not everyone feels sleepy when they are taken. Meanwhile, some people feel sleepy when they take second-generation antihistamines that do not cross the blood-brain barrier.

What is the strongest OTC antihistamine?

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

Get the word of drug information

After all, Claritin, Zyrtec, and Allegra are good antihistamines and are generally well tolerated. But there are some differences between the two, as noted above, that can make one of these antihistamines better than the others, depending on the person's needs and characteristics.

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