Antihistamines

Antihistamines block certain cells in the body from receiving histamine. Histamine is a chemical released by the immune system that causes the symptoms of an allergic reaction.

Nasal sprays

Antihistamine nasal sprays help relieve sneezing, an itchy or runny nose, sinus congestion, and postnasal drip.

Side effects of antihistamine nasal sprays might include a bitter taste and feeling very sleepy.

Examples of antihistamine nasal sprays include:

• Azelastine (Astepro).
• Olopatadine.

Eye drops

Antihistamine eye drops relieve itchy, red, swollen eyes. These eye drops may have a combination of antihistamines and other medicines. Some antihistamine eye drops require a prescription.

Side effects might include headache and dry eyes. If antihistamine eye drops sting or burn, try keeping them in the refrigerator. Or use refrigerated artificial tear drops before adding antihistamine eye drops.

Examples of antihistamine eye drops include:

• Ketotifen (Alaway, Zaditor).
• Olopatadine (Pataday).

Pills and liquids

Oral antihistamines ease many symptoms of allergies. These include a runny nose, itchy or watery eyes, hives, and swelling. Some of these medicines are available without a prescription.

Side effects include drowsiness, so use with caution if you need to drive or be alert.

Antihistamines that tend to cause drowsiness include:

• Diphenhydramine.
• Chlorpheniramine.
• Hydroxyzine.
• Brompheniramine.

Antihistamines much less likely to cause drowsiness include:

• Cetirizine (Zyrtec Allergy).
• Loratadine (Alavert, Claritin).
• Fexofenadine (Allegra Allergy).
• Levocetirizine (Xyzal Allergy 24HR).
• Desloratadine (Clarinex).

Please note that cetirizine and loratadine are still known to cause drowsiness in about 10% of people who take them.