Many people use antihistamines to treat allergy symptoms. Zyrtec (cetirizine) and Claritin (loratadine) are two popular brands. They contain different compounds but appear to be equally effective.

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

Zyrtec is a brand name for the drug cetirizine. Claritin is the brand name for loratadine. Zyretc and Claritin are in the same class of medications. Both are second-generation antihistamines and generally work the same way in the body. Neither is clearly better than the other.

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

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Zyrtec and Claritin are brand-name medications that people can buy over the counter (OTC). 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.

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.

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


Zyrtec and Claritin are effective for about 24 hours. A person should only take one dose per day. The body absorbs both antihistamines quickly, but Zyrtec seems to work faster for some people.

A 2019 article states that antihistamines reach their peak concentration between 30 minutes and 3 hours after swallowing them.

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

  • Allegra: This contains the active ingredient fexofenadine. Allegra is non-sedating, so drowsiness is not a common side effect, although it is possible. Allegra is also a second-generation antihistamine.
  • Benadryl: This contains the active ingredient diphenhydramine. This can last up to 24 hours, which is longer than the other three. It aims to treat minor skin reactions and seasonal allergies. Benadryl is a first-generation antihistamine, which makes it sedating, so people tend to feel drowsy after taking it.

When people come 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.

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

Side effects

Everyone reacts to medications differently, but Claritin and Zyrtec may have the following side effects:

Allergic reactions

Some people experience a severe allergic response called anaphylaxis after taking antihistamines. A person should 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 pharmacist and check the label carefully before giving antihistamines to a child.


A 2020 article examined the association between antihistamine use during early pregnancy and birth defects. Contrary to findings from older studies, the authors stated there was a lack of evidence to support an association.

The American College of Obstetricians and Gynecologists states that Zyrtec (citirizine) and Claritin (loratadine) may be safe during pregnancy.

The labeling for Zyrtec states that it is unsuitable during breastfeeding.

Pregnant people should check with a doctor before using an antihistamine or any other drug.

Claritin and Zyrtec are popular OTC antihistamines. Doctors consider them safe and effective treatments for minor allergies.

Both are second-generation antihistamines. These cause less drowsiness than first-generation antihistamines.

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.

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