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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 manufacturers usually market them for specific allergies.

Zyrtec is a brand name for the drug cetirizine. Claritin is the brand name for loratidine. Zyretc 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.

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People can purchase Zyrtec and Claritin without prescription. They are available as pills, chewable tablets, and syrups.

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

People can purchase Zyrtec, Claritin, and other popular brands 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.

Drowsiness

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.

Timescales

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 2014 study found that both drugs were absorbed into the bloodstream within 1–2 hours of taking the medication.

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. Allegra is also a second-generation antihistamine.
  • Benadryl contains the active ingredient diphenhydramine. This acts faster than the other three and aims to treat minor skin reactions, not seasonal allergies. Benadryl is a first-generation antihistamine, which makes it sedating, so people tend to feel drowsy after taking it.

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

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

Loratadine—present in Claritin—may not be safe for people with severe liver conditions. The liver has to break down loratadine. The kidneys break down cetirizine—found in Zyrtec—and the body excretes it in the 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 may have the following side effects:

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 check the label carefully before giving antihistamines to a child.

In 2012, a review found that some antihistamines may be problematic during pregnancy. However, the authors noted that there was no evidence linking cetirizine or loratidine to birth defects.

A study published in 2014 noted that 10–15 percent of women use antihistamines during pregnancy. Most appear to be safe, but some may have adverse effects.

The Centers for Disease Control and Prevention (CDC) urge people to ask a doctor before using an antihistamine or any other drug during pregnancy.

Claritin and Zyrtec are popular over-the-counter 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.