Before You Buy Benadryl

Facts About the Popular Cold and Allergy Remedy

woman holding cough syrup on a spoon, taking it to improve hostile cervical mucus
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Benadryl is a popular antihistamine drug that can be purchased over the counter without a prescription. It is effective in treating symptoms of the cold and mild allergy, including a runny nose, sneezing, hives, and itching. It is available in different generic formulations.

Benadryl works by blocking the effects of histamine, a substance released by the body involved in allergies. The drug usually starts to work within an hour.


Benadryl comes in a tablet, liquigel, syrup, chewable tablet, and topical cream formulation. The active ingredient is diphenhydramine, the amount of which can vary by formulation:

  • Allergy ULTRATAB - 25 milligrams (mg)
  • Dye-Free LIQUI-GELS - 25 mg
  • Allergy Plus Congestion - 25 mg
  • Children's Dye-Free Allergy Liquid - 12.5 mg per teaspoon (tsp)
  • Children's Allergy Free Plus Congestion - 12.5 mg per tsp
  • Children's chewable tablet - 12.5 mg per tablet


Benadryl is short-acting, meaning that it needs to be taken every four to six hours to ensure persistent relief. It is generally prescribed as follows:

  • For adults and children over 12, the standard dose is 25 mg to 50 mg taken every four to six hours, not to exceed six doses in 24 hours.
  • For children six to 12, a dose of 12.5 mg (one chewable tablet) to 25 mg (one adult tablet) may be taken every four to six hours, not to exceed six doses in 24 hours.
  • For children under six, Benadryl should not be given unless directed to do so by a pediatrician.

The topical cream can be used safely in adults and children over six, applied thinly over areas of rash but for no longer than seven days.

Side Effects of Benadryl

While Benadryl is effective in treating symptoms of the cold and allergy, there may be side effects. Most are mild and usually resolve within a few hours. The most common include:

  • Drowsiness
  • Dizziness
  • Nausea and vomiting
  • Headache
  • Muscle weakness
  • Excitability, primarily in children
  • Dry mouth, nose, and throat
  • Loss of appetite
  • Increased chest congestion
  • Constipation
  • Nervousness

Benadryl can impair your ability to function and should never be used if you are planning to drive. Many state laws will charge you with a DUI (driving under the influence) if you are deemed to have been impaired by Benadryl.

You should never drink alcohol when taking Benadryl as this can only enhance the effect. The same applies to any tranquilizers or sedatives.

Contraindications and Considerations

You should not use any topical cream containing diphenhydramine if you have chickenpox, measles, broken skin, or large areas of skin that need to be treated.

If you experience blurred vision, confusion, painful urination, or have difficulty urinating after taking Benadryl, call your doctor immediately.

Moreover, you should stop treatment and seek emergency care in the unlikely event you experience a potentially deadly, all-body reaction known as anaphylaxis (characterized by severe hives, difficulty breathing, abnormal heartbeat, and the swelling of the face, mouth, tongue, or throat).

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Article Sources
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  1. Benadryl. FAQ.

  2. Benadryl. Benadryl dosing guide.

  3. MedlinePlus. Diphenhydramine. Updated August 15, 2018.

  4. Consumer Reports. What can happen when you drive drugged? Updated January 5, 2016.

Additional Reading
  • U.S. National Library of Medicine. "Diphenhydramine." MedLine Plus. Bethesda, Maryland; updated October 24, 2017.