I think that this can be useful for someone to know. I was on the medicine called Zyrtec 10mg pills for 8 months. I gained 10 pounds. I took it for chronic urticaric. I stopped taking it 7 days ago. Today is actually day 7th. I've lost 5 pounds in 7 days, and have no itching, nor have my hives returned full force. Fortunately! I still have some hives, but no more than I was on the Zyrtec, just not as bad. I feel great, I have a lot more energy, but honestly I am still worried what will happen.
I am back on Zyrtec again. I stopped like you, but I found it impossible to stop taking it. I suffered from severe insomnia, back and stomach pains. After my 3rd night without sleep I gave in and went back on Zyrtec. Like you also, the weight I lost has now come back. I feel like I am addicted to Zyrtec medicine and I don't know how to stop it. I told to my Doctor and Pharmacist, and they claim that have never heard of this. So, I can’t give any advice.