Diphenhydramine Side Effects 

Side Effects of Diphenhydramine - for the Consumer 

Diphenhydramine/Phenylephrine 

All medicines may cause  side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side  effects persist or become bothersome when using Diphenhydramine/Phenylephrine: 

Constipation; diarrhea; dizziness; drowsiness; dry mouth, nose, or throat; excitability (especially in children); headache; loss of appetite; nausea; nervousness; restlessness; trouble sleeping; vomiting. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine/Phenylephrine: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision; chest pain; decreased coordination; difficulty urinating; fast or irregular heartbeat; fever; hallucinations; seizure; severe dizziness or drowsiness; severe nervousness, anxiety, restlessness, or trouble sleeping; tremors; unusual weakness. 

Diphenhydramine/Ibuprofen

All medicines can cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine/Ibuprofen: 

Constipation; diarrhea; dizziness; drowsiness; dry mouth, throat, and nose; excitability; gas; headache; heartburn; nausea; stomach pain or upset; thickening of mucus in nose or throat. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine/Ibuprofen: 

Severe allergic reactions (rash; hives; itching; trouble breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); bloody or black, tarry stools; change in the amount of urine produced; chest pain; confusion; dark urine; depression; fainting; fast or irregular heartbeat; fever, chills, or persistent sore throat; hallucinations; mental or mood changes; numbness of an arm or leg; one-sided weakness; red, swollen, blistered, or peeling skin; ringing in the ears; seizures; severe headache or dizziness; severe or persistent stomach pain or nausea; severe vomiting; shortness of breath; stiff neck; sudden or unexplained weight gain; swelling of hands, legs, or feet; tremor; unusual bruising or bleeding; unusual joint or muscle pain; unusual tiredness or weakness; vision or speech changes; vomit that looks like coffee grounds; wheezing; yellowing of the skin or eyes. 

Diphenhydramine

All medicines  may cause side effects, but many people have no, or minor, side  effects. Check with  your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine: 

Dizziness; drowsiness; dry mouth, throat, and nose; thickening of mucus in nose or throat. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine: 

Severe allergic reactions (difficulty breathing; hives; itching; tightness in the chest; rash; swelling of the mouth, face, lips, or tongue); decreased alertness; excitability; fast heartbeat; hallucinations; seizures; tightness or pounding in the chest; tremor; wheezing. 

Diphenhydramine/Pseudoephedrine 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine/Pseudoephedrine: 

Constipation; diarrhea; dizziness; drowsiness; dry mouth, nose, and throat; excitability; headache; loss of appetite; nausea; nervousness or anxiety; trouble sleeping; upset stomach; vomiting; weakness. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine/Pseudoephedrine: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision or other vision changes; fast or irregular heartbeat; fever, chills, or persistent sore throat; hallucinations; mood or mental changes; persistent trouble sleeping; restlessness; seizures;  severe dizziness, lightheadedness, or headache; severe drowsiness; tremor; trouble urinating or inability to urinate; unusual bruising  or bleeding. 

Diphenhydramine Capsules 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine Capsules: 

Dizziness; drowsiness;  dry mouth, throat, and nose; thickening of mucus in nose or throat. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine Capsules: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); convulsions; decreased alertness; excitability; fast heartbeat; hallucinations; tightness or pounding in the chest; tremor; wheezing. 

Diphenhydramine Chewable Tablets 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine Chewable Tablets: 

Dizziness; drowsiness; dry mouth, throat, and nose; thickening of mucus in nose or throat. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine Chewable Tablets: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); convulsions; decreased alertness; excitability; fast heartbeat; hallucinations; tightness or pounding in the chest; tremor; wheezing. 

Diphenhydramine/Phenylephrine Chewable Tablets 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine/Phenylephrine Chewable Tablets: 

Constipation; diarrhea; dizziness; drowsiness; dry mouth,  nose, or throat; excitability (especially in children); headache; loss of appetite; nausea; nervousness; restlessness; trouble sleeping; vomiting. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine/Phenylephrine Chewable Tablets: 

Severe allergic reactions (rash; hives; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision; chest pain; decreased coordination; difficulty urinating; fast or irregular heartbeat; fever; hallucinations; seizure; severe dizziness  and drowsiness; severe nervousness, anxiety, or restlessness; tremors; unusual weakness. 

Diphenhydramine/Pseudoephedrine Controlled-Release Capsules 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine/Pseudoephedrine Controlled-Release Capsules: 

Constipation; diarrhea; dizziness; drowsiness; dry mouth, nose, or throat; excitability (especially in children); headache; loss of appetite; nausea; nervousness; restlessness; trouble sleeping; vomiting. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine/Pseudoephedrine Controlled-Release Capsules: 

Severe allergic reactions (rash; hives; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision; chest pain; decreased coordination; difficulty urinating; fast or irregular heartbeat; fever; hallucinations; seizure; severe dizziness and drowsiness; severe nervousness, anxiety, or restlessness; tremors; unusual weakness. 

Diphenhydramine Cream 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine Cream: 

Skin irritation. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine Cream: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue). 

Diphenhydramine Dispersible Tablets 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine Dispersible Tablets: 

Dizziness; drowsiness; dry mouth, throat, and nose; excitability; thickening of mucus in nose or throat. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine Dispersible Tablets: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); convulsions; fast heartbeat or pounding in the chest; decreased alertness; hallucinations; tremor; wheezing. 

Diphenhydramine Elixir 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine Elixir: 

Dizziness; drowsiness; dry mouth, throat, and nose; excitability; thickening of mucus in nose or throat. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine Elixir: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); convulsions; fast heartbeat or pounding in the chest; decreased alertness; hallucinations; tremor; wheezing. 

Diphenhydramine/Pseudoephedrine Liquid 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine/Pseudoephedrine Liquid: 

Constipation; diarrhea; dizziness; drowsiness; dry mouth, nose, and throat; excitability; headache; loss of appetite; nausea; nervousness or anxiety; trouble sleeping;  upset stomach; vomiting; weakness. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine/Pseudoephedrine Liquid: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision or other vision changes; fast or irregular heartbeat; fever, chills, or persistent sore throat; hallucinations; mood or mental changes; persistent trouble sleeping; restlessness; seizures; severe dizziness, lightheadedness, or headache; severe drowsiness; tremor; trouble urinating or inability to urinate; unusual bruising or bleeding. 

Diphenhydramine/Phenylephrine Liquid 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine/Phenylephrine Liquid: 

Constipation; diarrhea; dizziness; drowsiness; dry mouth, nose, or throat; excitability (especially in children); headache; loss of appetite; nausea; nervousness; restlessness; trouble sleeping; vomiting. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine/Phenylephrine Liquid: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision;  chest pain; decreased coordination; difficulty urinating; fast or irregular heartbeat; fever; hallucinations; seizure; severe dizziness or drowsiness; severe nervousness, anxiety, or restlessness; tremors; unusual weakness. 

Diphenhydramine Lotion 

All medicines may cause side effects, but many people have no, or minor side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine Lotion: 

Skin irritation. 

Seek medical attention right away if  any of these SEVERE side effects occur when using Diphenhydramine Lotion: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in  the chest; swelling of the mouth, face, lips, or tongue). 

Diphenhydramine Orally Disintegrating Strips 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with  your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine Orally Disintegrating Strips: 

Dizziness; drowsiness; dry mouth, throat, and nose; thickening of mucus in nose or throat. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine Orally Disintegrating Strips: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); convulsions; decreased alertness; excitability; fast heartbeat; hallucinations; tightness or pounding in the chest; tremor; wheezing. 

Diphenhydramine Solution

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine Solution: 

Dizziness; drowsiness; dry mouth, throat, and nose; thickening of mucus in nose or throat. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine Solution: 

Severe allergic reactions (rash; hives; itching;  difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); convulsions; decreased alertness; excitability; fast heartbeat; hallucinations; pain, redness, or swelling at the injection site; tightness or pounding in the chest; tremor; wheezing. 

Diphenhydramine/Phenylephrine Strips 

All medicines may cause side effects, but many people have no, or minor side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine/Phenylephrine Strips: 

Constipation; diarrhea; dizziness; drowsiness; dry mouth; excitability; headache; loss of appetite; nausea; nervousness or anxiety; trouble sleeping; upset stomach; vomiting; weakness. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine/Phenylephrine Strips: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision or other vision changes; difficulty  urinating or inability to urinate; fast or irregular heartbeat; hallucinations; mood or mental changes; persistent trouble sleeping; restlessness; seizures; severe dizziness, lightheadedness, or headache; severe drowsiness; tremor. 

Diphenhydramine Suspension 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine Suspension: 

Dizziness; drowsiness; itching; dry mouth, throat, and nose; excitability; thickening of mucus in nose or throat. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine Suspension: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); convulsions; fast heartbeat or pounding in the chest; decreased alertness; hallucinations; tremor; wheezing. 

Diphenhydramine/Phenylephrine Suspension 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine/Phenylephrine Suspension: 

Constipation; diarrhea; dizziness; drowsiness; dry mouth, nose, or throat; excitability  (especially in children); headache; loss of appetite; nausea; nervousness; restlessness; trouble sleeping; vomiting. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine/Phenylephrine Suspension: 

Severe allergic reactions (rash; hives; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision; chest pain; decreased coordination; difficulty urinating; fast or irregular heartbeat; fever; hallucinations; seizure; severe dizziness and drowsiness; severe nervousness, anxiety, or restlessness; tremors; unusual weakness. 

Diphenhydramine/Hydrocodone/Phenylephrine Syrup 

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine/Hydrocodone/Phenylephrine Syrup: 

Dizziness; drowsiness, excitability; headache; nausea; nervousness or anxiety; trouble sleeping; weakness. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine/Hydrocodone/Phenylephrine Syrup: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); difficulty urinating; fast or irregular heartbeat; hallucinations; seizures; severe dizziness, lightheadedness, or headache; severe drowsiness; tremor. 

Diphenhydramine/Pseudoephedrine Tablets 

All medicines may cause  side effects, but many people have no,  or minor, side effects. Check with  your doctor if any of these most COMMON side effects persist or become bothersome when using Diphenhydramine/Pseudoephedrine Tablets: 

Constipation; diarrhea; dizziness; drowsiness; dry mouth, nose, and throat; excitability; headache; loss of appetite; nausea; nervousness or anxiety; trouble sleeping; upset stomach; vomiting; weakness. 

Seek medical attention right away if any of these SEVERE side effects occur when using Diphenhydramine/Pseudoephedrine Tablets: 

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision or other vision changes; fast or irregular heartbeat; fever, chills, or persistent sore throat; hallucinations; mood or mental changes; persistent trouble sleeping; restlessness; seizures; severe dizziness, lightheadedness, or headache; severe drowsiness; tremor; trouble urinating or inability  to urinate; unusual bruising or bleeding. 

Diphenhydramine Side Effects - for  the Professional 

Diphenhydramine 

The most frequent adverse reactions are underscored. 

• General:  Urticaria, drug rash, anaphylactic shock, photosensitivity, excessive perspiration, chills, dryness of the mouth, nose  and throat. 
• Cardiovascular System:  Hypotension, headache, palpitations, tachycardia, extrasystoles. 
• Hematologic System:  Hemolytic anemia, thrombocytopenia, agranulocytosis. 
• Nervous System:  Sedation, sleepiness, dizziness, disturbed coordination, fatigue, confusion, restlessness, excitation, nervousness, tremor, irritability, insomnia, euphoria, paresthesia, blurred vision, diplopia, vertigo, tinnitus, acute labyrinthitis, neuritis, convulsions. 
• GI System:  Epigastric distress, anorexia, nausea, vomiting, diarrhea, constipation. 
• GU System:  Urinary frequency, difficult urination, urinary retention, early menses. 
• Respiratory System:  Thickening of bronchial secretions, tightness of chest and wheezing, nasal stuffiness.