Cat hallucinating?

[Penelopepisspot]

I’m a bit worried about my cat. She’s 10.
Since last night she’s been behaving really strangely. She has been having episodes lasting about 20 minutes where she runs madly across the room, stops, grooms herself frantically for a couple of seconds, runs back to where she was, settles down for a second, runs madly again, madly grooms again, and so on. She looks quite freaked out.
Initially I thought that perhaps she’d been stung by a wasp or something, as she seemed to be grooming the same spot, but the more I watch her it appears that she is grooming different areas.
In between the episodes she’s behaving normally, purring, sitting on knees, eating/drinking normally.
Today it has escalated and she is now hissing at thin air during the episodes, almost as if she’s hallucinating and thinks she’s being chased or attacked.
The grooming and running is weird and erratic and nothing like her normal behaviour.
Has anyone come across anything like this before?

It’s happening every couple of hours.

I’m thinking it might be this
https://www.petplace.com/article/cats/pet-behavior-training/feline-hyperesthesia-fhs

It could be an allergic reaction to bites. Even if up to date with flea treatment, harvest mites (little red spider things) may bite before dying. As my vet told me today for a similar thing! My cat had a steroid injection to lessen the itching and scratching while he heals.

She doesn’t seem to have any obvious bumps of scabs from bites, but she is VERY fluffy so it’s hard to tell.
I really hope it is a temporary affliction, because she’s very distressed and unhappy.