Hi FB.
My Beau is older (15 this August) and has early arthritis too. He overgroomed his flank for years and although he does suffer from FAD which exacerbates the problem in flea season (when he starts on his tummy as well) he continued to overgroom when there are no fleas around at all. We all but gave up and accepted that he does this as habit.
Overgrooming becomes a habit because the fur is broken during excessive grooming which then turns stubbly and spikey, and this irritates the cat further (like when your newly shaved legs start to grow back and snag on things
)
Our vet told us it may be a comforter for him to groom the side that aches, so although Milly's showing no sign of discomfort at the vet, her arthritis may only occur to her when she's at rest and has nothing else on her mind (like new cat flaps or being taken the the vet for acupuncture every month?)
There are anti-depressants (a form of valium) called buspirone that your vet can prescribe if stress is believed to be the issue and a cause cannot be eliminated. These act to break the vicious cycle by stopping the stress long enough for the fur to recover and grow back soft and natural. To be honest I'd try a short course of these before subjecting my animals to frequent veterinary visits for acupunture - which I believe may create more stress than being dosed one tiny blue pill each day.
There is also the option of hormone treatment. Female hormones (similar to the Pill) are injected just once and can be extremely effective. However these are known to have potentially serious side effects so only your vet can advise if this is a good idea for Molly. I can definitely recommend it though as my Sammy benefitted hugely and has gone from a very nervy boy to a total love bunny and has stopped picking at an old scab on his shoulder which was forever flaring up due to his attentions!
You might also try a bitterant on her flank, such a Grannicks bitter apple spray. This is designed to stop puppies biting their stitches after surgery and works for some cats as well. I've had mixed success with my animals and Grannicks. Some utterly detest the taste and do stay away once they've tasted it (so its great for stopping them chewing wires and kittens from biting hands), but Beau just got on with cleaning it off so he could get back to his grooming habit.
Another option, of course, is physical exclusion i.e. a big collar. However these prevent catflap access and may increase stress so although it would physically prevent her from picking at the site it may make her more anxious. Worth bearing in mind though if all else fails. We have one of the "comfy collars" an inflatable alternative to the e-cone, which may serve to make hard work of her overgrooming habit?
Hope some of this rings a bell, there are so many issues that could be causing it, and it could be one of a hundred remedies that works for Milly, but do please persevere.
By the way. Beau has stopped overgrooming his flank recently since he had one of his fangs removed which had gone bad - so it may have been toothache all along that caused his stress
Nobody's perfect