Claritin vs Allegra: Which Non-Drowsy Antihistamine Should You Take?

Claritin vs Allegra at a Glance

Doses above are from the current U.S. Drug Facts or prescribing labels listed in Sources. Always follow the label on the package you buy, because store brands and formulations differ.

How They Work

Both block histamine H1 receptors, the switch histamine flips to cause sneezing, itching and a runny nose. As second-generation antihistamines, they cross into the brain much less than older drugs like diphenhydramine (Benadryl), which is why they’re labeled non-drowsy. Fexofenadine is actively pumped out of the brain by a transporter, which is one reason it has the cleanest drowsiness profile in its class. Loratadine is converted by the liver into an active metabolite (desloratadine, sold by prescription as Clarinex).

Which Works Better?

Head-to-head studies of loratadine and fexofenadine for seasonal allergies have generally found similar overall symptom relief, with some studies favoring fexofenadine for eye symptoms or speed of onset. Cetirizine (Zyrtec) often edges out both in potency studies, at the cost of more drowsiness; see Zyrtec vs Claritin and Allegra vs Zyrtec. Personal response varies a lot, so the best antihistamine is often the one that works for you.

One important limit: oral antihistamines do little for nasal congestion. If stuffiness is your main problem, a steroid nasal spray is usually more effective (see Flonase vs Nasacort), and allergy guidelines rank intranasal steroids as the most effective single treatment for persistent allergic rhinitis.

Drowsiness and Driving

Both are labeled non-drowsy. In clinical trials, fexofenadine’s sleepiness rates were similar to placebo even at higher-than-label doses. Loratadine is also rarely sedating at 10 mg, but its label notes that taking more than directed may cause drowsiness. A driving-simulator study found fexofenadine did not impair driving, unlike diphenhydramine. If you fly planes, drive professionally, or are very sensitive to sedation, fexofenadine is the usual pick.

Interactions You Should Know

• Fruit juice and Allegra: Grapefruit, orange and apple juice can significantly reduce fexofenadine absorption, so the label says take it with water and not with fruit juices.
• Antacids and Allegra: Aluminum- or magnesium-containing antacids (Maalox, Mylanta) lower absorption. Separate them by a couple of hours.
• Claritin: Few clinically important interactions at label doses. Some drugs that block liver enzymes (such as ketoconazole or erythromycin) raise loratadine levels; ask a pharmacist if you take prescription medicines.
• Doubling up: Don’t take two antihistamines together (for example Claritin plus Allegra, or either plus Benadryl or a nighttime cold product) unless a doctor advises it.

Children

Claritin’s 10 mg tablet is labeled for ages 6 and up; Children’s Claritin (5 mg per 5 mL liquid or 5 mg chewables) covers ages 2 to under 6 at a lower dose. Allegra’s 180 mg tablet is for 12 and up, and Children’s Allegra liquid covers ages 2 to 11 at 30 mg twice a day. Under 2, ask a pediatrician. Use the dosing cup that comes with the liquid.

Kidneys, Liver, Pregnancy and Older Adults

• Kidney disease: Both labels say ask a doctor; you may need a lower dose or less frequent dosing.
• Liver disease: The Claritin label says ask a doctor, since loratadine is processed by the liver.
• Adults 65+: The Allegra 180 mg label says ask a doctor; both are still far preferable to first-generation antihistamines in older adults.
• Pregnancy and breastfeeding: Both labels say ask a health professional. Loratadine has among the larger bodies of pregnancy safety data in its class, which is why clinicians often mention it, but get personalized advice.

Who Should Choose What

• Most sensitive to drowsiness, or need fast relief: Allegra, taken with water.
• Drink juice with breakfast or take antacids often: Claritin is simpler.
• Child aged 6–11 who can swallow tablets: Claritin 10 mg is labeled; Allegra tablets aren’t at 180 mg.
• Neither is enough: try cetirizine or add a steroid nasal spray, and see a clinician about allergy testing.
• Hives: second-generation antihistamines are first-line, but see a doctor for hives that last more than a few days or come with swelling of the lips or throat.

When to Talk to Your Doctor or Pharmacist

• Symptoms persist despite a week or two of daily use, or you need allergy medicine most of the year.
• You have kidney or liver disease, are 65 or older, pregnant or breastfeeding.
• Wheezing, shortness of breath, facial or throat swelling, or hives with trouble breathing: that’s an emergency.
• Sinus pain with fever, or symptoms that suggest infection rather than allergy.
• You want to stop after months to years of daily use and notice severe itching (reported mainly with cetirizine/levocetirizine).

Frequently Asked Questions

Sources

• DailyMed: Claritin (loratadine 10 mg) Drug Facts label
• DailyMed: Allegra Allergy (fexofenadine HCl 180 mg) Drug Facts label
• MedlinePlus: Loratadine
• MedlinePlus: Fexofenadine
• PubMed: Dresser et al., fruit juices inhibit organic anion transporting polypeptide-mediated drug uptake (fexofenadine)
• PubMed: Weiler et al., fexofenadine, diphenhydramine and alcohol on driving performance (2000)
• PubMed: loratadine vs fexofenadine seasonal allergic rhinitis comparative trials

Related Comparisons

• Zyrtec vs Claritin
• Allegra vs Zyrtec
• Xyzal vs Zyrtec
• Benadryl vs Claritin
• Flonase vs Nasacort
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