In this Article

• Introduction
• What's the difference between a controller and a reliever?
• What are antihistamines?
• How do antihistamines work?
• What are first generation antihistamines (OTCs)?
• What are second generation antihistamines (prescription)?
• What are common side effects of antihistamines?
• What are decongestants?
• How do decongestants work?
• When should I use topical decongestants?
• What are side effects of decongestants?
• What about combination antihistamine/decongestant preparations?
• Nasal Steroid Sprays
• Other nasal sprays that might help
• Tips for proper use of nasal sprays
• Nasal Allergy Medications At A Glance
• Nasal Allergy Medications Glossary
• Nasal Allergy Medications Index

What are common side effects of antihistamines?

Since the first generation antihistamines can penetrate the brain tissue, they generally cause more side effects than the second generation drugs, which usually cannot enter the central nervous system. Drowsiness is the most noticeable side effect, but this is sometimes desirable. For example, it may be useful when nighttime symptoms prevent restful sleep. During the day, however, this effect can cause problems.

Allergy Alert

Be cautious about driving a car or operating a machine when using OTC antihistamines. Do not take any tranquilizers or drink alcohol along with these drugs. The combination may promote more drowsiness. Also, check with your doctor before taking an antihistamine if you have glaucoma or thyroid, heart, or prostate problems.

The first generation antihistamines may also cause troublesome anticholinergic effects such as heart palpitations, difficulty urinating, constipation, dry mouth, and nervousness. These side effects usually occur when the medication is taken at higher than recommended doses.

The second generation of antihistamines currently on the market has few, if any, significant side effects at the recommended doses.

Allergy Assist

Antihistamines may be used for nasal symptoms in patients with asthma. It was previously thought that these drugs would dry up the airways in the patient's bronchial tubes and aggravate the asthma. However, there is no good evidence supporting this notion. Additionally, as you will learn, improving nasal symptoms may benefit patients with asthma.

Suggested Reading by Our Doctors

• diphenhydramine, Benadryl - Explains the medication diphenhydramine (Benadryl), a drug used for the relief of nasal and non-nasal symptoms of various allergic conditions such as seasonal allergic rhinitis.
• Chronic Rhinitis and Post-Nasal Drip - Information on post nasal drip and chronic rhinitis includes symptoms such as itchy runny nose, sneezing, itchy eyes, ears, and throat, and nasal congestion.
• fluticasone propionate nasal inhaler-spray, Flonase, Veramyst - Learn about the nasal spray drug fluticasone (Flonase, Veramyst) used to treat non-allergic and allergic rhinitis and its symptoms like a stuffy and runny nose.

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