Compare Benadryl vs. Robitussin DM

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


Robitussin Dm
(Guaifenesin / Dextromethorphan)

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.Breaks up mucus and relieves cough. Robitussin Dm (Guaifenesin / Dextromethorphan) is okay for loosening congestion in your chest and throat, but it could prevent you from coughing the mucus up. You have to take it more often than other guaifenesin products.
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Reviews & ratings
Button Group. All currently active
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Reviews for Benadryl (Diphenhydramine)
of people say Benadryl (Diphenhydramine) is worth it
say it works well
say it's a big hassle
Reviews for Robitussin Dm (Guaifenesin / Dextromethorphan)
10% vs. Benadryl (Diphenhydramine)
20% vs. Benadryl (Diphenhydramine)
+1% vs. Benadryl (Diphenhydramine)
Side effects
BenadrylRobitussin DM

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

FDA side effect reports for Benadryl »

We haven’t found good data for Robitussin DM side effects.

FDA side effect reports for Robitussin DM »
How it works
BenadrylRobitussin DM
Benadryl (Diphenhydramine) is an antihistamine. It blocks histamine, a chemical that causes congestion, itching, and other allergic reactions. It also makes you sleepy.Robitussin Dm (Guaifenesin / Dextromethorphan) is a combination medicine. Guaifenesin is an expectorant that breaks up and thins out mucus. Dextromethorphan is a cough suppressant.
Type of medication
BenadrylRobitussin DM
1st generation
Prescription or OTC
ExpectorantCough suppressantOver-the-counter
Available as
BenadrylRobitussin DM
  • Pill
  • Oral solution
  • Cream, gel, or ointment
  • Liquid
Used for (click to learn more)
BenadrylRobitussin DM
Risk factors for serious side effects
BenadrylRobitussin DM
  • 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 »
    • Using other medications that affect serotonin
      Detailed Robitussin Dm (Guaifenesin / Dextromethorphan) risks & warnings »
      Pregnancy category
      BenadrylRobitussin DM
      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
      NFDA pregnancy category (Unknown)

      The FDA hasn’t classified this medicine’s effects on unborn babies. Talk with your doctor about this medicine if you’re pregnant or planning on it.

      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.
      • People age 65 years and older have a higher risk of side effects from taking antihistamine medications like Benadryl (Diphenhydramine). Watch for changes in vision, severe dry mouth, trouble urinating, or constipation. The drowsiness caused by Benadryl (Diphenhydramine) can make you "unsteady" on your feet, leading to a higher chance of falls.
      No specific sleep-related info.
      No specific weight-related info.No specific weight-related info.
      Upsides and benefits
      BenadrylRobitussin DM
      • 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.
      • Robitussin Dm (Guaifenesin / Dextromethorphan) is a combination medicine that relieves multiple cold symptoms. It's good to use if you have chest congestion and a cough.
      • Helps loosen the mucus and phlegm that builds up and causes productive, wet coughs.
      Downsides and risks
      BenadrylRobitussin DM
      • 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.
      • Robitussin Dm (Guaifenesin / Dextromethorphan) isn’t useful if you have a dry cough without mucus or phlegm.
      • The two medications in this product could potentially work against each other. Guaifenesin makes mucus easier to cough up, while dextromethorphan (the "DM" in Robitussin Dm (Guaifenesin / Dextromethorphan)) stops you from coughing.
      • Needs to be taken more often during the day than other products with guaifenesin, like Mucinex.
      • Can cause sleepiness, dizziness, and an upset stomach.
      Tips from our pharmacists for people taking the medication
      BenadrylRobitussin DM
      • 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.
      • Drink plenty of fluids while taking Robitussin Dm (Guaifenesin / Dextromethorphan) because liquid helps break down mucus.
      • Cough suppressant starts working in 15 to 30 minutes.
      • Follow age-specific dosing instructions on how much to take. Don't take more than the recommended dose.
      • If your cough lasts more than 7 days, call your doctor.
      Learn more
      More about BenadrylSide effectsReviews & ratingsAlternativesFDA package insert
      More about Robitussin DMSide effectsReviews & ratingsAlternativesFDA package insert