I'm not an allergist, but I've suffered from allergies on and off throughout my life; thus I have a bit of personal experience as well as some facts gleaned through research.

1. Will you have to take this medicine (Zyrtec, or cetirizine) forever?
No one can tell you that. It depends on your allergies and the other steps you are taking to alleviate them.

2. Will your body acclimate to the medication and require an increased dosage?
I can find nothing in the literature to suggest that about this medication.

MIght I suggest....You say you developed allergies about a year ago. Instead of asking if you will have to take the medication forever and will your body acclimate, you might want to dig a little deeper. That is, you might want to ask yourself what changed to create this development.

For example:

Did you move to a new place, where pollen, plants, mold, carpet or furniture chemicals, a smoker next door, etc. could have triggered the allergies?

Did you suffer an illness that weakened your immune system?

Did you make a change in your diet, perhaps thus introducing a food allergy that is exacerbating overall allergic reactions?

Have you been under increased stress?

Or, has a lifetime of not-so-great health habits caught up with you? :-)

Years ago, while in the midst of an allergic reaction to a cat while staying at a friend's house, a nutritionist friend offered to me a drink of fruit juice, water, powered magnesium, and bit of liquid B vitamins. I had no faith that this concoction could address my convulsive sneezing and itchy eyes, but I figured it couldn't hurt me and I wanted to be polite. To my surprise, my allergic response stopped on a dime. You can read up on magnesium to learn more about how it can help some allergies.

I hope this helps.