Compare Benadryl vs. Phenylephrine

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

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Sudafed Pe

Treats allergy symptoms and helps you sleep. Benadryl (Diphenhydramine) is great for allergies, but curl up on the couch after taking it and get ready for a nap.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.
How it works
Benadryl (Diphenhydramine) is an antihistamine. It blocks histamine, a chemical that causes congestion, itching, and other allergic reactions. It also makes you sleepy.Sudafed Pe (Phenylephrine) is a decongestant. It narrows blood vessels and reduces swelling in your nasal passages to make breathing easier.
Type of medication
1st generation
Prescription or OTC
DecongestantPrescription or OTC
Available as
  • Pill
  • Oral solution
  • Cream, gel, or ointment
  • Pill
  • Nasal spray
  • Eye drops
  • Suppository
Used for (click to learn more)
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Reviews & ratings
Button Group. All currently active
Button Group. All currently active
Reviews for Benadryl (Diphenhydramine)
of people say Benadryl (Diphenhydramine) is worth it
say it works well
say it's a big hassle
Reviews for Sudafed Pe (Phenylephrine)
41% vs. Benadryl (Diphenhydramine)
34% vs. Benadryl (Diphenhydramine)
2% vs. Benadryl (Diphenhydramine)
Side effects

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

FDA side effect reports for Benadryl »

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

FDA side effect reports for Phenylephrine »
Risk factors for serious side effects
  • Using other drugs with the same ingredients
  • Age 65 years or older
  • Taking with alcohol
  • Taking other medicines that make you less alert
  • Children age 6 years and younger
  • Enlarged prostate
  • History of bladder problems
  • Glaucoma
  • Nursing mothers
Detailed Benadryl (Diphenhydramine) 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
BFDA pregnancy category (Probably safe)

Research studies with animals haven’t found a risk to unborn babies, but it hasn’t been properly studied in humans.

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
  • Don't take it with alcohol or other drugs that make you sleepy.
No specific alcohol-related info.
No specific food-related info.No specific food-related info.
Kidneys and liver
No specific kidneys and liver-related info.No specific kidneys and liver-related info.
No specific sex-related info.No specific sex-related info.
  • Benadryl (Diphenhydramine) makes you tired, so take it before you go to sleep.
  • Shouldn't use it before you want to sleep.
No specific weight-related info.No specific weight-related info.
Upsides and benefits
  • Benadryl (Diphenhydramine) is often better than other antihistamines at treating allergy symptoms and hives.
  • It can provide quick relief of allergy symptoms for both kids and adults.
  • It makes you sleepy, so it'll help if your allergies are bothering you at night.
  • The effects wear off in 4 to 6 hours, so side effects don't last that long.
  • It comes as a tablet, capsule, liquid, and quick dissolving tablet.
  • 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
  • Benadryl (Diphenhydramine) makes you more tired than Claritin, Allegra, or Zyrtec.
  • You shouldn't drive after taking Benadryl (Diphenhydramine) until you know how it affects you.
  • Talk to a pediatrician before giving Benadryl (Diphenhydramine) to a child.
  • It can increase the risk of falls, so elderly people shouldn't use Benadryl (Diphenhydramine).
  • Don't use Benadryl (Diphenhydramine) if you are breastfeeding.
  • 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
  • Take it as needed every 4 to 6 hours.
  • Benadryl (Diphenhydramine) can make you dehydrated, so avoid this side effect by drinking plenty of fluids.
  • Benadryl (Diphenhydramine) makes you tired, so take it before you go to sleep.
  • Don't take it with alcohol or other drugs that make you sleepy.
  • If you need to use it for more than a few weeks, talk with your doctor. A different medication might work better for you long-term.
  • If you only have itchy or watery eyes, try using just an antihistamine eye drop.
  • 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 BenadrylSide effectsReviews & ratingsAlternativesFDA package insert
More about PhenylephrineSide effectsReviews & ratingsAlternativesFDA package insert