Examples

Older (first-generation) over-the-counter and prescription antihistamines

Newer (second-generation) over-the-counter antihistamines

Newer (second-generation) prescription antihistamines

Antihistamines may be available as tablets, capsules, nasal sprays, or liquids. You can use them alone or combined with decongestants to treat allergic rhinitis.

How It Works

Many symptoms of allergic rhinitis, such as sneezing, itching, and runny nose, occur when your body releases a chemical called histamine. Antihistamine medicines block histamine and may reduce your symptoms.

Why It Is Used

You can use antihistamines to stop or reduce sneezing, runny nose, and watery and itchy eyes caused by an allergic reaction.

How Well It Works

All of these antihistamines work equally well to relieve sneezing, itching, and runny nose.

• Antihistamines begin to provide relief in 30 minutes to 2 hours.
• Antihistamines dry up the runny nose caused by allergies, but they usually do not clear up stuffiness.

Side Effects

The older (first-generation) antihistamines may:

• Make you sleepy or make it harder for you to concentrate.
• Affect your coordination, even when they do not make you drowsy.

Take care when using older antihistamines if you need to drive or operate dangerous or heavy machinery. After you take an antihistamine several times, you generally know when you will become sleepy. For some people the side effects become less severe after they take the medicine for a few days.

Other side effects may include:

• Dry mouth.
• A bitter taste in the mouth.
• Nausea and vomiting.
• Feeling restless or moody, especially in children.
• Inability to urinate (urinary retention).
• Blurred vision.
• Rapid heartbeat (tachycardia), from decongestants that combine antihistamines and decongestants.

Newer, second-generation antihistamines have fewer side effects. Many of the new antihistamines cause less drowsiness than older antihistamines or cause no drowsiness at all. Azelastine may cause drowsiness in some people, although this is not common.

Talk with your doctor before using antihistamines if you have:

• Glaucoma or other conditions that cause pressure inside the eye.
• Urinary problems due to an enlarged prostate.
• Thyroid conditions, such as an overactive or underactive thyroid.
• Liver, kidney, heart, or lung disease.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

The newer (second-generation) antihistamines tend to cost more than the older (first-generation) antihistamines. They do not work any better than the older antihistamines.

You may only have to take some of the newer antihistamines once a day.

In general, antihistamines don't relieve nasal congestion well. They are often combined with a decongestant in one product. Check with the doctor before giving these medicines to your child. Experts say not to give decongestants to children younger than 2.

Fexofenadine may cause menstrual cramps, nausea, and fatigue.

Older adults and women who are pregnant or breast-feeding should talk to their doctors before using antihistamines.

Azelastine has been approved for use in children older than age 12. Desloratadine ( Clarinex) may be suitable for children as young as 6 months. Children cannot use all antihistamines. Always talk with your doctor and check the label before you give antihistamines to children.

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