I've had no issues with the medication

You shouldn’t be itchy with it. One of its technical uses is actually to help with itch related to allergies. You could be allergic. Because Hydroxyzine is technically an antihistamine (allergy med- same as Benedryl & Claritin) it just has some sedating properties so it is also used for anxiety & anesthesia (via injection at a very high dose). But yes, you can build a tolerance and it doesn't work as well over time. I take it. And I have developed a bit of a tolerance too. It also helps with my allergies haha. Which is why it gets harder (for me) to discontinue.

Not itchiness but when I used to take it daily it stopped working over time. I got it switched back to as needed and it worked again

If your getting itchiness go back to drs and let them know you could be allergic x