Hi Amber,
Hair loss in cats can be due to a number of possible issues. It’s hard to be specific without knowing a lot more about Binx. The development of allergies is possible even after being normal for a number of years – environmental or food are at the top of that list. It’s even possible for indoor cats to get fleas. If there have been other changes in the home, stress or anxiety can be at fault. Oftentimes, this is called “psychogenic alopecia” and you can find more info about it where another pet owner has had a similar experience to you where their cat was biting and pulling out their hair.
Best of luck.
Dr. Ryan Llera