Benadryl vs. Mucinex DM

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

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Mucinex Dm
(Dextromethorphan / Guaifenesin)

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. Mucinex Dm (Dextromethorphan / Guaifenesin) is okay for loosening congestion in your chest and throat, but it could prevent you from coughing the mucus up. It comes as an extended-release tablet and a short-acting liquid.
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.Mucinex Dm (Dextromethorphan / Guaifenesin) is a combination medicine. Guaifenesin is an expectorant that breaks up and thins out mucus. Dextromethorphan is a cough suppressant.
Type of medication
1st generation
Prescription or OTC
Cough suppressantExpectorantOver-the-counter
Available as
  • Pill
  • Oral solution
  • Cream, gel, or ointment
  • Pill
  • Extended release
  • Liquid
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
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 Mucinex DM side effects.

FDA side effect reports for Mucinex DM »
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 »
    • Using other medications that affect serotonin
      Detailed Mucinex Dm (Dextromethorphan / Guaifenesin) 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
      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.
      No specific sleep-related info.
      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.
      • Mucinex Dm (Dextromethorphan / Guaifenesin) 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 in productive and wet coughs.
      • The extended release version of Mucinex DM lasts up to 12 hours.
      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.
      • Mucinex Dm (Dextromethorphan / Guaifenesin) 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 Mucinex Dm (Dextromethorphan / Guaifenesin)) stops you from coughing.
      • Can cause sleepiness, dizziness, and an upset stomach.
      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.
      • 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.
      • Drink plenty of fluids while taking Mucinex Dm (Dextromethorphan / Guaifenesin) because liquid helps break down mucus.
      • If your cough lasts more than 7 days, call your doctor.
      Learn more
      More about BenadrylSide effectsReviews & ratingsAlternativesFDA package insert
      More about Mucinex DMSide effectsReviews & ratingsAlternativesFDA package insert