Difference Between Allegra (Fexofenadine) and Zyrtec (Cetirizine)

Allegra vs Zyrtec (Fexofenadine vs Cetirizine)

Allegra and Zyrtec are very popular and frequently prescribed allergy medicine. They both come under the drug class second generation antihistamine drugs. The mechanism of action is to effect the histamine action inside the body; histamine is the chemical responsible for allergy response.


Allegra is also known by the trade name Allegra ODT and generic name Fexofenadine. This antihistamine drug is used commonly to reduce complications caused by allergic reactions. It is used to treat hay fever in children and adults. This drug can also reduce skin itching and hives which occur as results of chronic idiopathic urticaria. Allegra is available as tablets, capsules, and oral suspension. Tablets and capsules can be given to children who are at least 6 years old to treat seasonal allergy. Oral suspension can be administered to children from 2 to 11 years old and even two month old babies when treating chronic idiopathic urticaria. It is not known whether Allegra is harmful to unborn or nursing babies, therefore, it is advisable to seek medical advice just to be on the safe side.

Allegra should not be taken if a person shows any allergies to the drug. Antacids and any fruit juices should not be taken at least 15 minutes before and after the Allegra intake because antacids can reduce absorption of the drug. Other cold and allergy medicine, sedatives, muscle relaxers sleeping tablets, seizure medicine, anxiety medicine, and narcotic pain medicine should not be taken while taking Allegra because they tend to increase the sleepiness caused by Allegra. If it is very necessary, medical advice should be taken. Other than allergic reaction to medicine, minor side effects are associated with Allegra use such as nausea, stomach ache, diarrhea, headache, menstrual cramps, dizziness, and muscle pain.


Zyrtec is better known by its generic name Cetirizine and other trade names like “All day allergy” and Indoor/Outdoor allergy relief. This is used to treat allergic responses such as sneezing, watery nose, itching nose and throat etc. A person, while under medication, should not attend to work that requires being in alert as the drug tend to impair thinking and reacting. Alcohol should be strictly avoided because it increases the intensity of side effects.

Side effects such as uneven heart rate, insomnia, tremors, restlessness, confusion, blurred vision, dizziness, tired feeling, dry mouth, cough, constipation, nausea, less urination etc. are frequently associated with Zyrtec use. Some drugs such as other allergy medicine, narcotic pain medicine, muscle relaxers, seizure medicine, sleeping tablets should not be administered simultaneously because they can add to the sleepiness. Zyrtec has not shown any harmful effects to the unborn baby if taken during pregnancy but it has shown to harm the nursing baby if taken by a breast-feeding mother.

What is the difference between Allegra and Zyrtec?

• The drugs are two different chemicals and have slight differences in their side effects.

• Allegra’s effect on unborn is not known, but Zyrtec has a harmful effect on the unborn if a mother takes Zyrtec during pregnancy.