When hay fever or hives strike, most people reach for one of three over-the-counter antihistamines: Zyrtec, Claritin or Allegra. All three are “second-generation” antihistamines, which means they cause much less drowsiness than older ones like Benadryl, and one dose lasts 24 hours. But they aren’t identical. Here’s how they compare.
The quick comparison
- Zyrtec (cetirizine 10 mg): often works fastest, usually within an hour. It’s the most likely of the three to cause drowsiness, though most people feel fine.
- Claritin (loratadine 10 mg): the least likely to cause drowsiness. It may take a little longer to kick in, typically 1 to 3 hours.
- Allegra (fexofenadine 180 mg): also very unlikely to cause drowsiness, and works within about an hour. Take it with water only. Fruit juices like grapefruit, orange and apple can stop it being absorbed properly.
What they all treat
All three relieve the same symptoms of hay fever and other upper respiratory allergies:
- Sneezing
- Runny nose
- Itchy, watery eyes
- Itchy nose or throat
All three also relieve itching from hives.
Which one should you choose?
- You need to stay sharp (driving, studying, operating machinery): Claritin or Allegra are the safest bets for avoiding drowsiness.
- You want the fastest relief: Zyrtec or Allegra.
- One didn’t work well for you: it’s worth trying another. People respond differently, and switching often helps.
- You drink a lot of fruit juice in the morning: Zyrtec or Claritin may be easier than Allegra.
Tips for getting the most out of allergy tablets
- Take it before symptoms peak. If you know pollen season is coming, start a daily tablet a few days before. Antihistamines work best at preventing symptoms.
- Take one at the same time each day during allergy season.
- Don’t double up. Never take two of these antihistamines together, or more than one dose in 24 hours.
- Cut your exposure. Keep windows closed on high-pollen days, shower and change clothes after being outdoors, and wash bedding weekly in hot water.
When to see a doctor
- Your symptoms don’t improve after a few days of treatment
- You have wheezing, shortness of breath or chest tightness, which may be asthma
- You have liver or kidney disease, or you’re pregnant or breastfeeding
- You’re 65 or older (for Zyrtec), or buying for a child under 6
Get emergency help if hives come with swelling of the lips, tongue or throat, trouble breathing, or dizziness.
Shop allergy relief
- Zyrtec (Cetirizine) 10 mg
- Claritin (Loratadine) 10 mg
- Alavert (Loratadine) 10 mg
- Allegra (Fexofenadine)
This article is for general information only and isn’t a substitute for advice from a doctor or pharmacist. Always read the label before using any medicine.