Try some different OTC antihistamines, they may help too.
Your body doesn't grow resistant to the medicine, however over repeat exposures, your response to the allergen will increase. This increase in response will cause you to need a higher dose of the same medication to get the same level of relief.
Try and avoid the allergens all together or look into allergy shots which treats allergies at the immune response level.
i use 2 types of antihistamine for hayfever, i use them on alternative years - i find if i use the same one for 2 summers it does not work for the for the 3rd summer - but by alternating them i am fine.
I think you might. I've also been on zyrtec for a while and it seems to be less effective than it used to be... My sinus problems aren't that bad now though...although when my sinus problems fell off, my skin started acting up with hives and all. sigh.
Have you switched to a different antihistamine? I thought about doubling my dosage but that will cost me $60 a month on top of the nasal sprays etc. My doctor put me on it last year when I started breaking out in hives all over. I realized I had the fragrance allergy. I can control the fragrance part of it but had chronic sinus infections due to my other allergies after I took myself off it. I do nasal rinses, take nasal spray and try to minimize the allergens around me and it really feels like the Zyrtec doesn't little. And its not even spring allergy time in Minnesota!!!!!