Medical News Today: Zyrtec vs. Claritin for treating allergies

Many people use antihistamines to treat allergy symptoms. Zyrtec and Claritin are two of the most popular brands, but which is best?

Antihistamines can reduce allergy symptoms, such as watering eyes, itchy skin, hives, and swelling. They may also help with dermatitis or even mosquito bites, but are usually marketed for specific allergies.

Zyrtec and Claritin are in the same class of medications. Both are second-generation antihistamines, and they generally work the same way in the body. Neither is clearly better than the other.

In this article, we provide detail about the differences between Zyrtec and Claritin. We also compare them to two other popular brands of antihistamines: Benadryl and Allegra.

Zyrtec vs. Claritin

Zyrtec vs. claritin stock photo
Zyrtec and Claritin can be purchased without prescription and are available as pills, chewable tablets, and syrups.

Zyrtec and Claritin can be bought over the counter, and they are available in various forms, including pills, chewable tablets, and syrups.

Regardless of marketing claims, little scientific evidence shows that either is more effective.

Zyrtec, Claritin, and other popular brands can be purchased without a prescription from supermarkets, pharmacies, and online stores.

Active ingredients

Zyrtec and Claritin have different active compounds.

Zyrtec contains cetirizine hydrochloride, also called cetirizine HCL, while Claritin contains loratadine.


Zyrtec and Claritin are second-generation antihistamines. They are less likely to make a person feel drowsy or otherwise affect alertness than older, first-generation antihistamines.

However, Zyrtec is more likely to cause drowsiness than Claritin.

The labeling of Zyrtec says that a person should not take it when driving a vehicle or using machinery. Avoid taking Zyrtec with alcohol or other medicines that could cause drowsiness.


Zyrtec and Claritin are effective for about 24 hours. They should only be taken once per day. The body absorbs both antihistamines quickly, but Zyrtec seems to work faster for some people.

A 2014 study found that both drugs were absorbed into the bloodstream within 1–2 hours of taking the medication. Other studies suggest that most people respond to Zyrtec within 1 hour, while it can take 1–3 hours to respond to Claritin.

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Comparisons with other allergy medications

Researchers are often studying, comparing, and improving antihistamines. Other popular brands on the market today are Allegra and Benadryl.

  • Allegra contains the active ingredient fexofenadine. Allegra is non-sedating, so it should not make a person feel drowsy.
  • Benadryl contains the active ingredient diphenhydramine. This acts faster than the other three and is designed to treat minor skin reactions, not seasonal allergies. Benadryl is a sedating antihistamine, so people tend to feel drowsy after taking it.

How do allergy medications work?

When a person comes into contact with an allergen, their immune system reacts and produces a chemical called histamine.

Histamine causes many allergy symptoms, including inflammation of the skin or sinuses, pain, redness, and wheezing.

Immune responses also encourage extra mucus to develop, which helps to clear allergens from the nose and throat.

Allergy medications block histamine responses. This dulls the body’s response to minor or harmless allergens, such as pollen, dust, and pet dander.

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Zyrtec vs. claritin side effects
Zyrtec and Claritin are safe for most people with minor allergies, but side effects can include headaches and dizziness.

Claritin and Zyrtec are considered extremely effective and safe for most people with minor allergies. However, as with all medications, there are some potential side effects.

Loratadine may not be safe for people with severe liver conditions. The liver has to break down loratadine, while cetirizine is excreted in urine largely unchanged.

Claritin is more likely to interact with other drugs than Zyrtec. Claritin is broken down in the liver by enzymes that other drugs can inhibit. This may lead to Claritin building up in the body, which increases the risk of side effects.


Everyone reacts to medications differently, but Claritin and Zyrtec are associated with the following potential side effects:

Some people experience a severe allergic response called anaphylaxis after taking antihistamines. Seek emergency medical attention if any of the following symptoms are present:

  • hives
  • a swollen throat
  • swollen lips or face
  • trouble breathing or other respiratory symptoms
  • a racing heartbeat

Some antihistamines are safe for children, but it is a good idea to talk with a doctor or check the label carefully before giving antihistamines to a child.

A review from 2012 determined that using antihistamines during pregnancy may be problematic. Much research has established the safety of first-generation antihistamines, but less is known about the effects of second-generation brands like Claritin and Zyrtec on fetal development.

While the United Kingdom’s National Health Service state that loratadine and cetirizine should be safe to use during pregnancy, it is best to ask a doctor when considering any antihistamine.

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Claritin and Zyrtec are popular over-the-counter antihistamines. They are considered very safe and effective treatments for minor allergies.

Both are second-generation and cause less drowsiness than first-generation antihistamines. However, Zyrtec is more commonly associated with drowsiness than Claritin.

No research has concluded that Zyrtec or Claritin is more effective, but some people report better responses with one or the other. The slight differences between the two may make one drug more appropriate for some people.

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