Using Zyrtec for Treating Hives and Allergies

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Zyrtec (cetirizine) is an antihistamine in the class of drugs referred to as second-generation antihistamines. Antihistamines work by blocking histamines, chemical signals released by a type of cell in the immune system (mast cells) in order to alert other cells about a potential invader.

With allergies or hives, this is a case of mistaken identity in which the immune system is asked to respond to a harmless invader, such as tree pollen or dust mites. Zyrtec is recommended for children 2 years of age and older and adults. It is available as a tablet that can be swallowed, as a chewable tablet, and as a liquid.

A man's legs covered in an allergic reaction
Lode Kuylenstierna / EyeEm / Getty Images

First-generation antihistamines include medications such as Benadryl (diphenhydramine) and Vistaril/Atarax (hydroxyzine). These medications can be very effective for the treatment of hives or allergies but usually cause significant drowsiness which limits their use.

In addition to Zyrtec, other second-generation antihistamines include Xyzal (levocetirizine), Claritin (loratadine), and Allegra (fexofenadine).


Zyrtec is approved for the treatment of:

Zyrtec can be a good antihistamine for allergies and hives though it can cause sedation and fatigue in some people. These symptoms are usually milder than with the first generation antihistamines, but more pronounced than with medications such as Claritin or Allegra.

Overall, Zyrtec appears to be more effective for controlling allergies than Claritin or Allegra, but similar to Xyzal. However, every person with allergies is different, and it's often impossible to predict which medication will work best for any one person.

Zyrtec vs. Other Allergy Medications

Multiple studies show that Zyrtec is better at treating hay fever and hives when compared to Claritin (loratadine) or Allegra (fexofenadine). Zyrtec works faster, is more effective, and lasts longer than these other antihistamines.

When used for hives, Zyrtec may work better than Claritin or Allegra but is similar in effectiveness to Xyzal (levocetirizine) and Clarinex (desloratadine). Zyrtec, however, is more likely than Claritin or Allegra to have the side effect of fatigue.

Before Taking

If you are coping with hay fever or hives it's important to have a good relationship with your allergist. Some people try different medications while keeping an allergy journal as a way to see which medication works best for them specifically.

With children, it's important to weigh the benefits of treatments (including better concentration during school) against the possible risks and side effects.

Your pediatrician can help you recognize when your child may or may not benefit from medications. With older children, it can be very helpful to involve them and include them in this decision-making process.

During pregnancy, it's ideal if you don't take any medications, but sometimes that is not possible. The runny nose associated with pregnancy combined with allergic rhinitis can be very uncomfortable.

Zyrtec During Pregnancy

During pregnancy, those with allergic rhinitis or hives may notice a worsening of their symptoms, an improvement, or things may stay the same. The important point is that your symptoms may change and it can be helpful to be prepared.

Zyrtec has a pregnancy category "B" rating, meaning that it is generally considered to be safe for people who are pregnant. In contrast, some allergy medications should usually be avoided during pregnancy include intranasal antihistamines and first-generation antihistamines (such as Benadryl).


The dosage of Zyrtec is 2.5 milligrams (mg)—which is equivalent to 1/2 teaspoon—for children 2 to 6 years of age, and 5-10 milligrams for those aged 6 years and older. Larger doses have not been shown to be more beneficial for the treatment of hay fever, but may be more useful for the treatment of hives in some people.

Zyrtec starts to work within an hour or so after taking the medication—making it useful for the as-needed treatment of hay fever and hives. Taking it daily, however, may result in better overall control of allergy symptoms. This is in contrast to some medications, particularly nasal steroid sprays, which need to be taken for some time to be effective.

Side Effects

Zyrtec has a low incidence of side effects and is usually well-tolerated. Common side effects include:

  • Sedation: Sleepiness occurs in around 14% of people
  • Fatigue: Fatigue occurs in roughly 5% to 6% of people
  • Dizziness
  • Dry mouth

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By Daniel More, MD
Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and currently practices at Central Coast Allergy and Asthma in Salinas, California.