Compare Allegra vs. Phenylephrine

Head-to-head comparisons of medication uses, side effects, ratings, and more.

Allegra
(Fexofenadine)

Sudafed Pe
(Phenylephrine)

Treats allergy symptoms. Allegra (Fexofenadine) relieves allergy symptoms without making you feel drowsy.Clears your sinuses. Sudafed Pe (Phenylephrine) is a good medication for relieving stuffy nose. It doesn't work as well as pseudoephedrine (Sudafed), but it has fewer side effects.
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Reviews & ratings
Button Group. All currently active
Button Group. All currently active
5.2727272727272725Allegra
Reviews for Allegra (Fexofenadine)
77%
of people say Allegra (Fexofenadine) is worth it
59%
say it works well
0%
say it's a big hassle
Reviews for Sudafed Pe (Phenylephrine)
44%
33% vs. Allegra (Fexofenadine)
23%
36% vs. Allegra (Fexofenadine)
10%
10% vs. Allegra (Fexofenadine)
Side effects
AllegraPhenylephrine
  • Vomiting 3%
  • Headache 3%
  • Cough 3%
  • Back pain 2%
  • Ear, nose, or throat infection 2%
  • Diarrhea 1%
  • Fever 1%
  • Runny nose 1%
  • Dizziness 1%
  • Stomach discomfort 1%
More Allegra side effects »

We haven’t found good data for Phenylephrine side effects.

FDA side effect reports for Phenylephrine »
How it works
AllegraPhenylephrine
Allegra (Fexofenadine) is an antihistamine. It blocks histamine, a chemical that causes congestion, itching, and other allergic reactions.Sudafed Pe (Phenylephrine) is a decongestant. It narrows blood vessels and reduces swelling in your nasal passages to make breathing easier.
Type of medication
AllegraPhenylephrine
Antihistamine
2nd generation
Prescription or OTC
DecongestantPrescription or OTC
Available as
AllegraPhenylephrine
  • Pill
  • Dissolving tablet
  • Liquid
  • Pill
  • Nasal spray
  • Eye drops
  • Suppository
Used for (click to learn more)
AllegraPhenylephrine
Risk factors for serious side effects
AllegraPhenylephrine
  • Taking with alcohol
  • Taking other medicines that make you less alert
  • History of phenylketonuria (PKU)
Detailed Allegra (Fexofenadine) risks & warnings »
  • History of high blood pressure
  • Taking MAO inhibitors
  • History of heart problems
  • Age 65 years or older
  • Women of childbearing age
Detailed Sudafed Pe (Phenylephrine) risks & warnings »
Pregnancy category
AllegraPhenylephrine
CFDA pregnancy category (Weigh risks vs. benefits)

Research studies with animals found harmful effects on unborn babies. It hasn’t been properly studied in humans. The benefits might outweigh the risks even if you’re pregnant. Talk with your doctor.

See the FDA package insert
CFDA pregnancy category (Weigh risks vs. benefits)

Research studies with animals found harmful effects on unborn babies. It hasn’t been properly studied in humans. The benefits might outweigh the risks even if you’re pregnant. Talk with your doctor.

See the FDA package insert
Alcohol
No specific alcohol-related info.No specific alcohol-related info.
Food
No specific food-related info.No specific food-related info.
Kidneys and liver
  • The dose needs to be adjusted for people with kidney problems.
No specific kidneys and liver-related info.
Sex
No specific sex-related info.No specific sex-related info.
Sleep
  • Won't make you feel drowsy like some antihistamine medicines.
  • Shouldn't use it before you want to sleep.
Weight
No specific weight-related info.No specific weight-related info.
Upsides and benefits
AllegraPhenylephrine
  • Relieves allergy symptoms, like sneezing, runny nose, and itching.
  • Approved to be used in kids and adults age 6 months and older.
  • Won't make you feel drowsy like some antihistamine medicines.
  • Available over-the-counter without a prescription.
  • Comes in many forms, such as a tablet, liquid, or quick-dissolving tablet.
  • It's okay to take with most other medications since it has very few interactions.
  • Works to clear nasal congestion and helps you breathe better.
  • Helpful in relieving congestion-related headaches.
  • Has fewer side effects than other decongestants like pseudoephedrine.
  • It doesn't raise your blood pressure and heart rate as much, or cause as much trouble falling asleep.
  • Doesn't give you rebound congestion (worse symptoms when you stop taking it) like nasal spray decongestants do.
Downsides and risks
AllegraPhenylephrine
  • For some people, the effects Allegra (Fexofenadine) has on allergies will wear off over time.
  • May not work as well as the first-generation antihistamines, like diphenhydramine (Benadryl).
  • The dose needs to be adjusted for people with kidney problems.
  • Phenylephrine doesn't last as long as other decongestants like pseudoephedrine (Sudafed).
  • You shouldn't use it if you have high blood pressure.
  • Can make your heart race or make you feel anxious and restless.
  • Shouldn't use it before you want to sleep.
  • Not as effective after using it for 4 days in a row.
Tips from our pharmacists for people taking the medication
AllegraPhenylephrine
  • Starts working in 1 to 2 hours depending on what dosage form you're taking.
  • Works best when taken regularly, even before symptoms are expected to appear.
  • Can make you feel dizzy or sleepy, so you can take it at bedtime.
  • Follow age-specific dosing and don't take more than recommended.
  • If symptoms get worse or you need to use it for more than a few weeks, talk with your doctor.
  • Starts working in 30 minutes.
  • Phenylephrine can make you restless, so don't take it too close to bedtime.
  • It's in other cold and flu combination medicines. Read labels closely so you don't accidentally double up and take too much of it in a day.
  • Follow age-specific dosing instructions on how much to take.
  • Let your doctor know if your symptoms don't improve in a few days.
Learn more
More about AllegraSide effectsReviews & ratingsAlternativesFDA package insert
More about PhenylephrineSide effectsReviews & ratingsAlternativesFDA package insert