Active Ingredients
Claritin contains loratadine, a second-generation antihistamine. Zyrtec contains cetirizine, also a second-generation antihistamine. Both block histamine to reduce allergy symptoms like sneezing, itching, and runny nose, but cetirizine binds more tightly to histamine receptors, potentially making it stronger for some users.
Effectiveness and Onset
Zyrtec often works faster—relief starts in about 1 hour versus Claritin's 1-3 hours—and may control symptoms better for hives or severe itching in studies. Claritin provides smoother 24-hour coverage without as much daytime impact for milder allergies.
Drowsiness Levels
Zyrtec causes drowsiness in up to 14% of users due to slight blood-brain barrier crossing. Claritin rarely causes it (under 2%), making it preferable for driving or daytime use.
Duration and Dosing
Both last 24 hours in adults:
- Claritin: 10 mg once daily.
- Zyrtec: 5-10 mg once daily (or 5 mg for kids).
| Feature | Claritin (Loratadine) | Zyrtec (Cetirizine) |
|---------------|-----------------------|---------------------|
| Onset | 1-3 hours | ~1 hour |
| Drowsiness | Minimal | Moderate (10-14%) |
| Best for | Mild allergies, non-drowsy needs | Severe symptoms, hives |
Side Effects and Safety
Common for both: headache, dry mouth. Zyrtec adds fatigue or dizziness more often. Avoid alcohol with either. Safe for kids over 2 (syrups available); Claritin approved from 6 months in some forms. Both non-prescription in the US.
Cost and Availability
Generic versions make both cheap—$10-20 for 30-day supply. Zyrtec slightly pricier generics sometimes. No patents block generics now; both OTC since early 2000s.
Which to Choose
Pick Claritin for no-drowsiness priority or mild seasonal allergies. Go Zyrtec for quicker, stronger relief despite sedation risk. Trial both; switch if one underperforms. Consult a doctor for persistent symptoms or interactions (e.g., with sedatives).