Your doctor may recommend an antihistamine for the relief of allergy symptoms. These medications are used to treat allergic conditions, such as hay fever, hives, pet allergies, and mold allergies.

Antihistamines work by counteracting the effects of histamine - a substance released by the body during an allergic reaction. By preventing histamine's effects, antihistamines reduce allergic symptoms like stuffy nose, watery eyes, skin rash, and other annoyances.

Antihistamines are available over-the-counter (OTC) or by prescription from your doctor and multiple formulations, including tablet, liquid, or nasal spray.

Nonsedating Antihistamines

Older forms of antihistamines, such as diphenhydramine (Benadryl®) and chlorpheniramine (Chlor-Trimeton®) are known to have sedating effects, while newer antihistamaines, such as Allegra®, Xyzal®, or Zyrtec®, are referred to as "nonsedating antihistamines".

These nonsedating formulations are less likely to cause such drowsiness.

Side Effects of Antihistamines

Common side effects of all antihistamines include:

  • Dry mouth, throat, or nose
  • Digestive difficulties, stomach-ache, or nausea
  • Difficulty urinating
  • Constipation
  • Restlessness or irritability (especially in children)

Before using antihistamines, it's a good idea to tell your doctor about the different types of allergies you have. Take special precautions before giving antihistamines to children, such as paying attention to label directions and warnings, because some serious side effects are more likely to occur in infants and young children than in adolescents and adults. Take similar care when giving antihistamines to elderly people.

© 2010 Vivacare. Last updated June 8, 2013.

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