If you’re one of the 60 million Americans with allergic rhinitis, you might hesitate to venture outdoors once spring arrives[1]. During this time, outdoor allergens such as pollen are abundant, often leading to uncomfortable allergy symptoms like sneezing, itchy/watery eyes, itchy throat and nasal congestion.
But even with seasonal allergies (or hay fever), it’s possible to enjoy the warmer weather. Taking an over-the-counter (OTC) antihistamine, a medication that blocks the effects of allergens on your immune system, can keep uncomfortable allergy symptoms at bay.
Here’s what you need to know about common OTC antihistamine brands and side effects.
What Is an Antihistamine?
Antihistamines are a class of drugs used to alleviate symptoms such as swelling, itching, redness and increased mucus production that are caused by an allergic reaction. They do this by blocking the effect of histamine, a chemical produced by mast cells in the immune system in response to allergens such as pollen, pet dander, mold and dust. Antihistamines help combat allergic reactions by blocking the receptors that bind histamine.
Specifically, antihistamines can be used to treat the following, according to Brian Staiger, Pharm.D., a clinical pharmacist in Buffalo, New York and owner of HelloPharmacist.com:
- Hay fever or allergic rhinitis (seasonal allergies)
- Allergic conjunctivitis (redness and itching of the eyes)
- Hives/urticaria (itchy raised bumps on the skin)
- Itchiness from skin conditions like eczema or atopic dermatitis (itchy, dry and scaly skin)
Their main use, however, is to prevent perennial or seasonal allergy symptoms, says Dr. Staiger, noting that antihistamines work best when taken before exposure to a potential allergen.
For anaphylactic food allergy reactions, antihistamines should only be used as an add-on therapy to epinephrine, adds Purvi Parikh, M.D., a board-certified allergist and immunologist at the Allergy and Asthma Network in Fairfax, Virginia and a Forbes Health Advisory Board member. That’s because food allergy reactions can be life-threatening, and antihistamines don’t work fast enough to alleviate symptoms.
Differences Between First- and Second-Generation Antihistamines
First-generation antihistamines, such as Benadryl (diphenhydramine) and Chlor-Trimeton (chlorpheniramine), are noted for their relatively short duration of action—meaning they only provide relief from symptoms for around four to six hours per dose, says Dr. Staiger.
Because first-generation antihistamines cross the blood-brain barrier, they can cause sedation, drowsiness, fatigue and impaired concentration and memory.
Second-generation antihistamines, such as Claritin (loratadine), Allegra (fexofenadine) and Zyrtec (cetirizine) were developed to avoid or minimize these unwanted central nervous system side effects, notes Dr. Staiger.
Additionally, second-generation antihistamines can be effective for up to 24 hours and are often utilized and strongly preferred for daily use to prevent or treat allergy symptoms, he adds.
Note that different antihistamines are appropriate for different age ranges—and in many cases, OTC antihistamine brands offer formulations specifically designed for kids. Be sure to speak with your child’s pediatrician about which OTC allergy medicine may be best for them.
Additionally, the American College of Obstetricians and Gynecologists (ACOG) notes that there are some antihistamines that are considered generally safe to take during pregnancy, but recommends pregnant individuals consult their health care provider before taking an OTC allergy medication.
For lactating individuals, antihistamines are generally considered safe while breastfeeding with short-term or occasional use. That said, small amounts are known to pass into breast milk, so be sure to seek advice from your provider before taking any antihistamines.
First-Generation Antihistamine Brands
Benadryl
Benadryl (diphenhydramine) is the strongest and most effective first-generation antihistamine, says Roberto Garcia-Ibáñez, M.D., a board-certified allergist and immunologist at The Allergi Group in Tampa, Florida. It’s often administered in the emergency room to treat an allergic reaction, he adds.
Benadryl is generally used to treat allergy symptoms such as congestion, sneezing, runny nose, itchy/watery eyes and hives; it may also be used for insomnia, vertigo and motion sickness. Its available forms include capsule, tablet, oral solution and intravenous or intramuscular injection, and lasts four to six hours.
Chlor-Trimeton
Chlor-Trimeton (chlorpheniramine) helps treat cold and allergy symptoms such as itchy/watery eyes, sneezing, itchy nose/throat and runny nose. It is also used to treat motion sickness. It’s available as a tablet, capsule, chewable tablet and oral solution. Chlor-trimeton isn’t as strong as Benadryl, but it lasts around eight hours, according to Dr. Staiger.
Second- and Third-Generation Antihistamine Brands
Zyrtec
Zyrtec (cetirizine) is the strongest of the second-generation antihistamines, says Dr. Garcia-Ibáñez. And because there is less chance of toxicity with this medication, the dosage can be increased substantially, at the discretion of your doctor, he says.
Zyrtec is an effective treatment for allergy symptoms and hives. It’s available as a tablet, capsule, oral solution and orally disintegrating tablet, and typically lasts up to 24 hours. Although Zyrtec causes less drowsiness than first-generation antihistamines, it’s technically not “non-drowsy,” informs Dr. Staiger, as it causes drowsiness in 10% of people.
Claritin
Claritin (loratadine) is a non-drowsy second-generation antihistamine that treats seasonal allergy symptoms such as itchy eyes, runny nose and sneezing; it’s also effective for hives. It’s available as a liquid-filled capsule, tablet, chewable or orally dissolving tablet and oral suspension and it typically works for 24 hours.
Allegra
Allegra (fexofenadine) is used to treat seasonal allergy symptoms like sneezing, itchy/watery nose and itchy/watery eyes, as well as chronic hives. It’s available as a tablet, orally disintegrating tablet or oral suspension and is typically effective for up to 24 hours. Allegra is generally the least-sedating second-generation antihistamine.
Side Effects of Antihistamines
Potential side effects of antihistamines include:
- Vision changes, such as blurry vision
- Decreased appetite
- Dizziness
- Sleepiness (more likely with first-generation antihistamines)
- Dry mouth
- Feeling excited, nervous or irritable
If you’re experiencing drowsiness to the point of being unable to stay awake, confusion, urinary retention or dehydration, seek immediate medical attention, advises Dr. Parikh.
