Understanding allergies

People with seasonal allergies or hay fever know all about the aggravating symptoms, from the runny or congested nose to the watery eyes, sneezing, and itching. These symptoms occur when you’re exposed to allergens such as:

  • trees
  • grass
  • weeds
  • mold
  • dust
  • animal dander
  • smoke

Allergens cause certain cells throughout your body, called mast cells, to release a substance called histamine. Histamine binds to H1 receptors in your nose and eyes to open blood vessels and increase secretions. This action causes your runny nose, watery eyes, sneezing, and itching.

Allegra Allergy and Claritin are both antihistamines. They work by blocking histamine from binding to H1 receptors. In turn, this action helps prevent your allergy symptoms. While these drugs work similarly, they do have some differences such as in who they can treat, the forms they come in, and what side effects are possible.

Drug features

Both Allegra Allergy and Claritin treat the following symptoms:

  • sneezing
  • runny nose
  • itchy, watery eyes
  • itchy nose and throat

Claritin, though, also treats hives and itchiness.

The active ingredient in Allegra Allergy is fexofenadine. The active ingredient in Claritin is loratadine.

Both drugs conveniently come in a variety of forms available over the counter. These include an orally disintegrating tablet, oral tablet, and oral capsule. Claritin also comes in a chewable tablet and oral solution, and Allegra also comes as an oral suspension. However, these forms are approved to treat different ages. If you’re treating your child, this could be an important distinction in making your choice. Do not use either drug in children who are younger than the form is approved for.

FormAllegra AllergyClaritin
Orally disintegrating tabletages 6 years and olderages 6 and older
Oral suspensionages 2 years and older---
Oral tabletages 12 years and olderages 6 years and older
Oral capsuleages 12 years and olderages 6 years and older
Chewable tablet---ages 2 years and older
Oral solution---ages 2 years and older

For specific dosage information for adults or children, read the product package carefully or talk to your doctor.

Side effects and warnings

Allegra Allergy and Claritin are considered newer antihistamines. They’re less likely to cause drowsiness than older antihistamines. The side effects of Allegra and Claritin are similar, but most people don’t experience any side effects with either drug. The following table lists examples of possible side effects of Allegra Allergy and Claritin.

Mild side effectsAllegra Allergy Claritin
trouble sleeping
dry mouth
sore throat
Possible serious side effectsAllegra Allergy Claritin
swelling of your eyes, face, lips, tongue, throat, hands, arms, feet, ankles, and lower legs
trouble breathing or swallowing
chest tightness
flushing (reddening and warming of your skin)


Allegra Allergy and Claritin interact with similar drugs. Specifically, they may interact with ketoconazole and erythromycin. Allegra can also interact with antacids, and Claritin can also interact with amiodarone. Make sure you tell your doctor about all prescription and OTC drugs, herbs, and supplements you take.

Claritin and Allegra can also cause problems if you have kidney disease. Certain forms may be dangerous if you have phenylketonuria. These include the orally disintegrating tablets of Allegra and the chewable tablets of Claritin. You should also talk to your doctor about the safety of Claritin if you have liver disease.

Pharmacist’s advice

Both Claritin and Allegra Allergy work well to treat allergies. In general, they’re tolerated well by most people. They have different active ingredients, forms, dosing, possible side effects, and warnings. Work with your doctor to choose the one that’s best for you.

Before taking either medication, talk to your doctor. Ask what other steps you can take to reduce your allergy symptoms.