As I suffer from severe hay fever (particularly severe: birch pollen), I have already tried and compared cetirizine tablets from various manufacturers. I can't say whether they work differently for each person. What I can say, however, is that they all work differently and also make you feel tired to varying degrees. Cetirizine 10 from 1A Pharma has achieved second place in my personal ranking for its effect against allergies and hardly makes me tired at all (my first place in terms of effectiveness unfortunately has the negative characteristic of making me very tired). Accordingly, 1A Pharma offers me the best overall package and the price is also perfectly acceptable (in my personal test, there were also cetirizine tablets that cost 2.5 times as much, made me tired and yet hardly helped me against hay fever). So much for my experience with this product.