Allertec and Zyrtec contain the same active ingredient: cetirizine hydrochloride, typically in a 10 mg tablet. Allertec is a store-brand version sold by Kirkland Signature (Costco) that is marketed directly as a comparison to Zyrtec’s active ingredient. In practical terms, they do the same thing.
Same Drug, Different Label
Both products deliver 10 mg of cetirizine hydrochloride per tablet. Zyrtec is the original brand name, manufactured and marketed by UCB Pharma across dozens of countries. Allertec (often labeled “Aller-Tec”) is Kirkland Signature’s store-brand equivalent, sold at Costco at a lower price point. The packaging itself states “Compare to Zyrtec® active ingredient.”
The key difference is cost. Brand-name Zyrtec carries a premium because of name recognition and marketing. Allertec offers the same dose of the same medication for less. This is the same dynamic you see with virtually every over-the-counter drug that has a generic or store-brand counterpart.
How Generic Equivalence Works
For a generic version of any drug to be sold in the United States, the FDA requires proof that it performs the same way in the body as the brand-name version. For cetirizine, this means a single-dose crossover study in healthy adults, measuring cetirizine levels in the blood after taking the generic versus the brand-name tablet. The generic must fall within a 90% confidence interval of the original, meaning the body absorbs and processes it at essentially the same rate and to the same extent.
This standard applies to the active ingredient. Inactive ingredients (fillers, coatings, dyes) can differ between brands. For the vast majority of people, these differences don’t matter. If you have a known sensitivity to a specific dye or filler, it’s worth comparing the inactive ingredient lists on both packages, but the therapeutic effect is the same.
What Cetirizine Treats
Cetirizine is a second-generation antihistamine. It works by blocking the body’s histamine response, which is what causes allergy symptoms like sneezing, runny nose, itchy or watery eyes, and throat irritation. It’s also used to treat hives, the itchy red welts that can appear on the skin.
These uses apply equally whether you’re taking Zyrtec or Allertec. The medication is effective against seasonal allergies (pollen from trees, grasses, and ragweed) and year-round triggers like dust mites, pet dander, and mold.
Side Effects to Expect
Because the active ingredient is identical, the side effect profile is the same for both products. The most common one is drowsiness, which affects more than 1 in 10 people. Cetirizine is classified as a second-generation antihistamine, meaning it causes less sedation than older options like diphenhydramine, but it’s still noticeably more sedating than some newer alternatives.
Other side effects that occur in more than 1 in 100 people include headaches, dry mouth, nausea, dizziness, diarrhea, and a sore throat. These tend to be mild and often ease as your body adjusts to the medication.
Which One Should You Buy
If you’re choosing between Allertec and Zyrtec purely on effectiveness, there is no meaningful difference. You’re paying for the same 10 mg cetirizine tablet either way. Most pharmacists will tell you the same thing: the store brand works identically to the name brand for antihistamines like this. The only reason to prefer Zyrtec specifically is personal preference or if you need a formulation (like liquid or dissolvable tablets) that a particular store brand doesn’t offer. For standard 10 mg tablets, Allertec is a straightforward substitute.