Allergies Home > Benadryl Side Effects

Although most people do not experience problems while taking Benadryl, it's possible to have side effects. Based on the limited information from prescription Benadryl products, common side effects may include drowsiness, heartburn, and dizziness. While most side effects of Benadryl are minor, some are potentially serious and should be reported to your healthcare provider immediately, including blurred vision, difficulty urinating, and loss of balance.

An Introduction to Benadryl Side Effects

As with any medicine, Benadryl® (diphenhydramine hydrochloride) can cause side effects. However, not everyone who takes the medication will have problems. In fact, some people tolerate it quite well. If side effects do occur, in most cases, they are minor and either require no treatment or can easily be treated by you or your healthcare provider.
(This article covers many, but not all, of the possible side effects with Benadryl. Your healthcare provider can discuss a more complete list of Benadryl side effects with you.)

Possible Side Effects of Benadryl

Benadryl is a relatively "old" medication, approved before the United States Foods and Drug Administration (FDA) required very detailed side effect information in the prescribing information for medications. This is the case with prescription Benadryl products; only vague side effect information (with no specific percentages) is provided. Additionally, the non-prescription Benadryl products have almost no information about potential side effects listed on the label (as is standard with non-prescription products).
Based on the limited information from prescription Benadryl products, the most common side effects of Benadryl are thought to include:
  • Sedation (a feeling of sleepiness and reduced anxiety)
  • Drowsiness
  • Dizziness
  • Coordination problems
  • Indigestion or heartburn
  • Thickening of bronchial secretions (chest mucus).
Other reported side effects include:
  • Sensitivity to the sun
  • Excessive sweating and/or chills
  • Dry mouth, nose, or throat
  • Fatigue
  • Restlessness, excitation, nervousness, or irritability
  • Shakiness (tremor)
  • Insomnia
  • An unusual, pleasant feeling (euphoria)
  • Unusual sensations, such as tingling or numbness
  • A spinning sensation (vertigo)
  • Loss of appetite, nausea, or vomiting
  • Diarrhea or constipation
  • Nasal stuffiness
  • Early menstrual period.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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