CLARITIN vs ZYRTEC
Independent side-by-side comparison.
Neither is clearly "better" — Zyrtec (cetirizine) and Claritin (loratadine) are both second-generation antihistamines that work the same way and relieve allergy symptoms about equally well, so the choice comes down to drowsiness versus how fast it kicks in.
The key difference
They're clinically similar, not the same drug: both are second-generation antihistamines that block histamine, and the NHS says "there's not much evidence to suggest any particular antihistamine is better than any other at relieving allergy symptoms." The one consistent real difference is drowsiness — the NHS cetirizine page notes cetirizine "seems to be more likely to make you feel sleepy than loratadine" (and the NHS loratadine page says the reverse: loratadine is "less likely to make you feel sleepy than cetirizine"). Onset differs slightly too: the NHS says you should feel better "within an hour" of cetirizine versus "within 1 to 3 hours" of loratadine. Both are still classed as non-drowsy/less-sedating second-generation antihistamines (MedlinePlus groups Zyrtec and Claritin together as ones that "cause less sleepiness than others").
Choose Zyrtec (cetirizine) if
Either is fine for everyday hay fever, hives, and allergy symptoms — but lean to Zyrtec (cetirizine) if you want the faster effect (NHS: relief usually within an hour) and aren't bothered by, or actually wouldn't mind, a bit more sleepiness.
Choose Claritin (loratadine) if
Lean to Claritin (loratadine) if staying alert matters most (driving, work, school), since the NHS says it's less likely than cetirizine to make you feel sleepy — accepting that it may take a little longer (1 to 3 hours) to kick in.
Which is better for…
| Situation | Better choice | Why |
|---|---|---|
| Fastest relief today | Zyrtec (cetirizine) | Onset is roughly 60 minutes for cetirizine vs ~75 minutes for loratadine, and cetirizine is measurably more effective 1.5 hours after the dose. |
| Non-drowsy / daytime / driving or work | Claritin (loratadine) | Loratadine does not enter the brain appreciably and does not cause drowsiness at the recommended dose; Allegra (fexofenadine) is a comparable non-drowsy option. |
| Hives / itchy skin | Zyrtec (cetirizine) | Both are FDA-labeled for chronic hives and are first-choice options; cetirizine is generally considered somewhat more potent for itch and wheals, so it is often the pick when hives are the main problem. |
| Everyday long-term allergy control | Either — both work | Both are once-daily, 24-hour second-generation antihistamines suitable for ongoing seasonal or perennial allergy control; pick by drowsiness tolerance and speed. |
| Nighttime (sedation is OK or wanted) | Zyrtec (cetirizine) | Cetirizine is the most sedating of the second-gen antihistamines (sleepiness in roughly 10–15%), so taking it at bedtime can turn that drawback into a non-issue; alcohol intensifies the effect. |
| Kids | Either — both work | Both come in children's forms and are used for pediatric allergies, but dosing is strictly by product and age — follow the package label or your pediatrician rather than an adult rule of thumb. |
| Severe allergic reaction (throat/breathing/whole-body) | Neither — epinephrine + call 911 | Anaphylaxis needs epinephrine immediately; antihistamines work too slowly and do not reverse airway swelling or low blood pressure, and relying on them can dangerously delay the only treatment that helps. |
General guidance for choosing between two over-the-counter options, not a personal recommendation — follow each product’s Drug Facts label and ask a pharmacist if you have a health condition or take other medicines.
Bottom line
Similar, not a clear winner: same drug class, comparable allergy relief per the NHS. Pick by side-effect/speed tradeoff — Claritin (loratadine) if you want the least chance of drowsiness, Zyrtec (cetirizine) if you want faster relief and don't mind being a touch more likely to feel sleepy. If one doesn't suit you, it's reasonable to try the other. Follow the OTC Drug Facts label and ask a pharmacist or doctor if you have kidney/liver disease, are pregnant or breastfeeding, or take other medicines.
This is not a summary of either drug’s FDA label, and it is not complete. Both labels carry warnings, contraindications and interactions that are not on this page. Read the label for the drug you are actually taking — we link both above — and take the decision to your prescriber.
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Frequently asked questions
What is the difference between Claritin and Zyrtec?
Claritin contains Loratadine, while Zyrtec contains Cetirizine Hydrochloride — they have different active ingredients.
What is the downside of taking Zyrtec?
Cetirizine is the most sedating of the second-generation antihistamines: sleepiness is reported in roughly 10–15% of users (about 14% in labeling data), and alcohol can intensify that drowsiness. It is still far less sedating than first-generation Benadryl, but if daytime alertness matters, loratadine or fexofenadine cause less drowsiness.
What is the downside of Claritin?
Loratadine trades speed and raw potency for its non-drowsy profile. It starts working more slowly than cetirizine (about 75 minutes vs ~60), and in head-to-head studies cetirizine reduced allergy symptoms more (roughly 34% vs 14% overall). For stubborn hives or when you need relief fast, Claritin may underperform.
Is it better to take Zyrtec in the morning or night?
It is a once-daily, 24-hour medicine, so either time gives all-day coverage. Because cetirizine is the second-gen antihistamine most likely to cause drowsiness, taking it at night is a reasonable choice if it makes you sleepy; if it doesn't affect you, morning is fine. Take it at the same time each day.
Is Zyrtec or Claritin better for post nasal drip?
Both treat allergic rhinitis, including its post-nasal drip. Cetirizine (Zyrtec) tends to act a bit faster and reduces overall nasal symptoms more than loratadine in head-to-head studies, so it is a reasonable first try — but no trial has shown a post-nasal-drip-specific advantage, and post-nasal drip from a cold or non-allergic irritation may not respond to any antihistamine.
Ratings are based on FDA regulatory (recall-safety) data. This comparison is for general reference only — not medical advice. Always consult a licensed professional before choosing or switching a medication.