Benadryl Side Effects

Generic name: diphenhydramine

Note: This page contains information about the side effects of diphenhydramine. Some of the dosage forms included on this document may not apply to the brand name Benadryl.

In Summary

More frequent side effects include: sedation and thickening of bronchial secretions. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to diphenhydramine: oral capsules and tablets, parenteral injection

Side effects include:

Sedation, sleepiness, dizziness, disturbed coordination, epigastric distress, thickening of bronchial secretions.

For Healthcare Professionals

Applies to diphenhydramine: compounding powder, injectable solution, oral capsule, oral disintegrating strip, oral liquid, oral tablet, oral tablet chewable, oral tablet disintegrating

General

The most commonly reported side effects included somnolence, dizziness, and incoordination.^[Ref]

Nervous system

Common (1% to 10%): Sedation/somnolence/sleepiness, drowsiness, unsteadiness, dizziness, headache, attention disturbance
Rare (0.01% to 0.1%): Extrapyramidal effects, tremor, convulsions
Frequency not reported: Paresthesia, dyskinesia/muscle dyskinesia, vertigo, neuritis, incoordination, psychomotor impairment, activation of epileptogenic foci^[Ref]

Drowsiness usually diminishes after a few days.^[Ref]

Gastrointestinal

Common (1% to 10%): Dry mouth
Frequency not reported: Gastrointestinal disturbance, nausea, vomiting, constipation, diarrhea, dyspepsia, epigastric distress^[Ref]

Other

Common (1% to 10%): Fatigue
Frequency not reported: Lassitude, tinnitus, acute labyrinthitis, asthenia, chills, impaired performance (including impaired driving, work, and/or information processing)^[Ref]

Psychiatric

Rare (0.01% to 0.1%): Confusion, depression, sleep disturbances
Frequency not reported: Paradoxical excitation/excitation, agitation, increased energy, restlessness, nervousness, euphoria, anxiety, hallucinations, insomnia, irritability^[Ref]

Cardiovascular

Rare (0.01% to 0.1%): Palpitations, hypotension, arrhythmia
Frequency not reported: Tachycardia, chest tightness, extrasystoles^[Ref]

Hematologic

Rare (0.01% to 0.1%): Blood disorders
Frequency not reported: Hemolytic anemia, thrombocytopenia, agranulocytosis^[Ref]

Hypersensitivity

Rare (0.01% to 0.1%): Hypersensitivity reactions
Frequency not reported: Angioedema, anaphylactic shock^[Ref]

Hepatic

Rare (0.01% to 0.1%): Liver dysfunction^[Ref]

Dermatologic

Frequency not reported: Rash, urticaria, skin rashes, erythema, photosensitivity, pruritus, drug rash, excessive perspiration^[Ref]

Respiratory

Frequency not reported: Dyspnea, thickening of bronchial secretions, throat tightening, wheezing, nasal stuffiness, dry nose or throat^[Ref]

Genitourinary

Frequency not reported: Urinary hesitancy/difficulty/retention, dysuria, early menses^[Ref]

Ocular

Frequency not reported: Blurred vision, dry eyes, diplopia^[Ref]

Metabolic

Frequency not reported: Increased appetite, anorexia^[Ref]

Musculoskeletal

Frequency not reported: Muscle twitching/weakness^[Ref]

Not all side effects for Benadryl may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.