Find out everything you need to know about antihistamines. What symptoms they treat, who should take them and who should not.
Check your symptoms
Antihistamines treat:
- sneezing
- runny nose
- watery eyes
- itchiness
- scratchy throat
Frequency and Duration for Antihistamines
There are prescription and non-prescription antihistamines. They can last anywhere from 4 to 24 hours. Over the counter antihistamines used for occasional cold symptoms usually need to be taken every 4-6 hours.
Length of Use for Antihistamines
You should not take an over the counter antihistamine for more than 7 days before talking to your doctor. If your symptoms last longer than 7 days, you may have developed something more serious.
Important things to tell your doctor
You should tell your doctor if you have any of the following before taking an antihistamine:
- asthma or chronic bronchitis
- high blood pressure
- glaucoma
- liver disease
- kidney disease or difficulty urinating
- prostate problems
- ulcers or other stomach problems
- other chronic illnesses
- pregnant, trying to get pregnant or breastfeeding
- ALL medications you are taking, including herbal supplements
Common Antihistamines
Some common names for antihistamines are:
Over the counter
- Benadryl - diphenhydramine (generic)
- Claritin - loratidine (generic)
- Zyrtec - ceterizine (generic)
- Triaminic - chlorpheniramine (generic) - for children
Prescription
- Allegra - fexofenadine (generic)

