Allegra generally starts working about 1 hour after you take it. The effects of a 60 mg dose last about 12 hours, and a 120 mg or 180 mg dose last about 24 hours.

Active Ingredients: In each tablet: Fexofenadine HCl (180mg). Inactive Ingredients: Colloidal Silicone Dioxide, Croscarmellose Sodium, Hypromellose, Iron Oxide Blends, Magnesium Stearate, Microcrystalline Cellulose, Polyethylene Glycol, Povidone, Pregelatinized Starch, Titanium Dioxide.

The chances of experiencing drowsiness with Allegra are very low. In fact, it's one of the antihistamines that's least likely to make you feel sleepy. But drowsiness with Allegra is still possible. The risk of drowsiness is higher if you also take other medications that make you tired, or if you drink alcohol.

Fexofenadine is an antihistamine medication that comes in a capsule or tablet form. It treats and prevents symptoms of allergies like itchy eyes, sneezing and hives. It works by blocking histamine in your body. A common brand name of this medication is Allegra®.

Adults and children 12 years of age and over: Take one 180 mg tablet with water once a day; do not take more than 1 tablet in 24 hours. Children under 12 years of age: do not use. Adults 65 years of age and older: ask a doctor.

Yes, you can take fexofenadine (Allegra) only when you need it if you have allergy symptoms once in a while. But if you have allergy symptoms on a daily basis, taking it regularly is more likely to give you the most relief from your allergies. Can I take fexofenadine (Allegra) if I'm pregnant?

An antihistamine that works to relieve allergy symptoms of sneezing, runny nose, itchy/watery eyes, and itchy nose or throat due to hay fever or other upper respiratory allergies.

Antihistamines work by blocking a substance called histamine in your body. Histamine is known for causing allergy symptoms. Blocking it helps prevent symptoms of seasonal allergies or hay fever. Both Allegra and Zyrtec are effective at treating allergy symptoms and take a similar amount of time to start working.

“Antihistamines help with itching and sneezing, but alone do nothing to help the congestion that keeps you up at night.” Decongestants are the “D” part in allergy medications like Allegra-D®, but they can have a stimulant effect that disrupts sleep in some people.

Directions. Adults and children 12 years of age and over: Take one 180 mg tablet with water once a day; do not take more than 1 tablet in 24 hours. Children under 12 years of age: do not use.

Call your doctor if your symptoms do not improve after 7 days of treatment, or if you have a fever with a headache, cough, or skin rash. If you need surgery or medical tests, tell the surgeon or doctor ahead of time if you have taken a cold or allergy medicine within the past few days.

Allegra works within two hours and Zyrtec works within one hour. Several studies have found cetirizine (Zyrtec) to be more effective than fexofenadine (Allegra) at relieving symptoms of allergic rhinitis and urticaria, and it appears to have a longer duration of action.