Weird red spots and puking

For the last 6 months my puss has being getting these weird raised red spots in little clusters, the vet has no idea what it is.
The fur around it falls out then it bleeds off and on for a few days and finally it heals up.

Other than that, she's healthy.

Apart from throwing up her biscuits all over the show.
She used to be a 100% biscuit girl and then we finally found a canned food she'd eat and now we can't feed her biscuits as she pukes them up about 30 minutes after eating them.
Once again, the vet is scratching his head.

Sounds like an allergy to me. Possibly a food allergy. Are the red spots located around the face, by any chance? That's usually a telltale sign of a food allergy.

Yet I would think that a vet would at least mention this...

Also, did you introduce the canned food around 6 months ago --- around the same time that you began to notice the red spots?

I agree that it sounds like an allergy. I'd suggest maybe getting a second opinion from another vet, maybe he/she will find something that your vet missed?

This guy is the only vet around here. I swear the vets in this country are hopeless.
Also the only canned food that you can get in the shops is all fish based and all containing tuna, she's been eating it about a year after we finally found one she liked.
The spots themselves appear at various point on her main body, none on her face or tail.
I thought they were an insect of some kind but apparently not.
This guy won't even take a biopsy.
I'll see if I can take a photo sometime today.
Not sure why she's throws up the biscuits, they're the same brand she's always eaten since kittenhood.