What is diphenhydramine?
Diphenhydramine is an antihistamine that reduces the effects of natural chemical histamine in the body. Histamine can produce symptoms of sneezing, itching, watery eyes, and runny nose.
Diphenhydramine is used to treat sneezing, runny nose, watery eyes, hives, skin rash, itching, and other cold or allergy symptoms.
Diphenhydramine is also used to treat motion sickness, to induce sleep, and to treat certain symptoms of Parkinson’s disease.
Diphenhydramine may also be used for purposes not listed in this medication guide.
Before taking this medicine
You should not use diphenhydramine if you are allergic to it.
Ask a doctor or pharmacist if it is safe for you to take diphenhydramine if you have other medical conditions, especially:
- blockage in your digestive tract (stomach or intestines);
- bladder obstruction or other urination problems;
- a colostomy or ileostomy;
- liver or kidney disease;
- asthma, chronic obstructive pulmonary disease (COPD), or other breathing disorder;
- cough with mucus, or cough caused by smoking, emphysema, or chronic bronchitis;
- heart disease, low blood pressure;
- a thyroid disorder; or
- if you take potassium (Cytra, Epiklor, K-Lyte, K-Phos, Kaon, Klor-Con, Polycitra, Urocit-K).
It is not known whether diphenhydramine will harm an unborn baby. Ask a doctor before using this medicine if you are pregnant.
Diphenhydramine can pass into breast milk and may harm a nursing baby. Antihistamines may also slow breast milk production. Ask a doctor before using this medicine if you are breast-feeding.
Older adults may be more likely to have side effects from this medicine.
How should I take diphenhydramine?
Use diphenhydramine exactly as directed on the label, or as prescribed by your doctor. Do not use in larger or smaller amounts or for longer than recommended. Cold or allergy medicine is usually taken only for a short time until your symptoms clear up.
Do not give diphenhydramine to a child younger than 2 years old. Always ask a doctor before giving a cough or cold medicine to a child. Death can occur from the misuse of cough and cold medicines in very young children. You should not use diphenhydramine to make a child sleepy.
Measure liquid medicine with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.
For motion sickness, take diphenhydramine 30 minutes before you will be in a situation that causes you motion sickness (such as a long car ride, airplane or boat travel, amusement park rides, etc). Continue taking diphenhydramine with meals and at bedtime for the rest of the time you will be in a motion-sickness situation.
As a sleep aid, take diphenhydramine within 30 minutes before bedtime.
Call your doctor if your symptoms do not improve after 7 days of treatment, or if you have a fever with a headache, cough, or skin rash.
This medication can affect the results of allergy skin tests. Tell any doctor who treats you that you are using diphenhydramine.
Store at room temperature away from moisture and heat.