What do I need to know about antihistamines?

When You Take Antihistamines

  • Antihistamines work best when taken before you’re exposed to allergens.
  • They work by preventing histamines from attaching to certain sites on cells and causing symptoms.
  • Over-the-counter antihistamines and some prescription antihistamines can cause drowsiness. Be sure you know when it’s safe to use them.
  • Don’t drink alcohol while taking antihistamines.
  • Don’t take antihistamines without your doctor’s approval if you’re pregnant, trying to get pregnant, or nursing.

For more than 50 years, antihistamines have been the first type of medication chosen to treat nasal allergies. They are a great way to head off symptoms before they start. They are especially effective against runny noses, sneezing, and itching. However, they do little to relieve nasal congestion.

Many antihistamines are available without a prescription, and some are quite inexpensive. These can, however, cause drowsiness or sedation. There are newer prescription antihistamines available that don’t cause as much drowsiness. These include the drugs Zyrtec (cetirizine), Allegra (fexofenadine), and Claritin (loratadine). See what’s the difference between sedating and nonsedating antihistamines? to learn more.


How do I take antihistamines?

Antihistamines come in tablet, capsule, liquid, and injectable forms. They’re available over the counter (OTC) or by prescription. Because antihistamines don’t help stuffy noses, they’re often sold in combination with decongestants.

To learn more about antihistamines, read the next few articles pertaining to the following:

  • sedating versus nonsedating
  • how to use antihistamines safely
  • how antihistamines work
  • side effects


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