Generic name: Fexofenadine

Allegra is a nonsedating antihistamine. Antihistamines block the effects of histamine, a body chemical that causes swelling and itching. It is safer than the related antihistamine Seldane when used in conjunction with erythromycin, Nizoral, and several similar drugs; it is also safe for people with liver disease.

Quick Facts About Allegra


Used to relieve hay fever and its symptoms: itchy, runny nose, sneezing, and itchy, watery eyes. Effects of medication begin in 1 hour and last 12 hours.

Allegra Dosage

Take exactly as prescribed.

  • Usual adult dose: 1 tablet (60 milligrams) taken 2 times per day.
  • Usual child dose: not prescribed for children under 12 years.
  • Missed dose: take as soon as possible, unless almost time for next dose. In that case, do not take missed dose: go back to regular schedule. Do not double doses.

Allegra Side Effects

Overdose symptoms:

none reported. However, if you suspect an overdose, immediately seek medical attention.

More common side effects: cold or flu, drowsiness, fatigue, menstrual problems, nausea.

Less common Allegra side effects: No known less common or rare side effects.


Drug interactions rare.

Inform your doctor before combining Allegra with:

Erythromycin (E.E.S., ERYC, EryTab, Erymax, Erythocin, and others); or ketoconazole (Nizoral). May increase the blood levels of Allegra.

No known food/other substance interactions.

Special Cautions

While human studies are lacking, risk cannot be ruled out. If pregnant, planning to become pregnant, or breastfeeding, inform your doctor immediately. Potential benefits may justify the potential risk in using the medication.

No special precautions apply to seniors.

Not prescribed for children under 12 years.

  • Do not take more frequently than every 12 hours.
  • Take only for allergies, unless otherwise advised by your doctor.
  • Take half the usual dose If you have a kidney problem.
  • If a pounding heartbeat or fainting occurs, inform your doctor immediately.

Note: provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Allegra side effects, please contact your healthcare provider.