Decongestants and Antihistamines

What are decongestants and antihistamines?

Decongestants relieve a stuffy nose. Antihistamines help dry up a runny nose. These medicines are often confused with each other because they are both used to help runny, stuffy noses. However, they are different and do not act the same way on your body.

Many nonprescription cold and allergy products contain several types of medicines. They may treat many symptoms. It can be confusing trying to figure out which medicine to choose. Ask your pharmacist or healthcare provider if you are not sure which medicine is best for your symptoms.

How do they work?

Decongestants narrow the blood vessels in the nose. This reduces swelling and makes it easier for you to breathe. It also may reduce the amount of mucus made by your nose. You can buy some decongestants without a prescription. The most common types are:

• pseudoephedrine (Sudafed)
• phenylephrine (Neo-Synephrine).

Antihistamines block the effect of histamine. Histamine is a chemical your body makes when you have an allergic reaction. It causes redness and swelling. By blocking the effects of histamine, antihistamines help decrease congestion, watery eyes, sneezing, and runny nose. Common antihistamine medicines are:

• diphenhydramine (Benadryl)
• chlorpheniramine (Chlor-Trimeton)
• cetirizine (Zyrtec)
• fexofenadine (Allegra)
• loratadine (Claritin)
• desloratadine (Clarinex).
• azelastine (Astelin).

When are they used?

Decongestants are often used to treat:

• colds
• ear or sinus infections.

Antihistamines are most often used to treat symptoms of allergies. These include:

• sneezing and runny nose from hay fever
• itching, swelling, and redness from hives or other allergic rashes.

What should I watch out for?

Decongestants

Decongestants work by making your blood vessels smaller. They can also increase your heart rate and your blood pressure. Because of this effect on your heart and blood pressure, you should not take a decongestant without first checking with your healthcare provider if you have:

• heart disease
• high blood pressure
• glaucoma
• thyroid disease
• trouble urinating or an enlarged prostate
• diabetes.

Antihistamines

A common side effect of antihistamines is drowsiness. Some types are less likely than others to make you drowsy. This may not be a problem if a dose at bedtime is all you need. Or you might try the medicine for several days despite the drowsiness. Often the drowsiness goes away after you have taken the drug for 3 to 5 days.

Some "nonsedating" antihistamines are available. These antihistamine medicines usually do not cause drowsiness. Some require a prescription, but you can buy some without a prescription. They work well for most people, but they tend to cost more than other antihistamines.

If you have any of the following medical problems, you should check with your provider before taking antihistamines:

• glaucoma
• hyperthyroidism (overactive thyroid gland)
• high blood pressure
• enlarged prostate
• heart disease
• ulcers
• stomach or intestinal blockage
• liver disease
• kidney disease
• bladder obstruction
• diabetes.

Taking antihistamines with other medicines, such as antidepressants or sedatives, may cause problems. Read the labels carefully. Ask your provider or pharmacist if you have any questions.

If you are pregnant, talk with your healthcare provider before taking these medicines.