Allegra (fexofenadine) usually starts to work in about 1 hour, with most people feeling clear relief by 1–2 hours after a dose. Its effect then lasts around 12–24 hours, depending on the strength you take.

Quick Scoop

  • Most people notice some allergy relief (sneezing, runny nose, itchy eyes) within 1–2 hours of taking Allegra.
  • Product information for Allegra 24‑hour tablets states it starts working in one hour and then provides all‑day relief.
  • Typical 60 mg doses last about 12 hours, while 120–180 mg “24‑hour” versions are designed to last up to 24 hours.
  • If taken daily, some people find symptoms improve more steadily over several days of consistent use, especially during heavy allergy seasons.

If you do not feel any benefit after a full day of correct dosing, or your symptoms are severe (trouble breathing, swelling, wheezing), seek medical care urgently rather than just taking more medicine.

Information gathered from public forums or data available on the internet and portrayed here.