Has anyone used a hepa/air purifier for cat allergies?

[samstownsunset]

Any good?

My mum has to have a cat in her life despite being allergic to them!

I was thinking of getting her one of these pet air purifiers but do they make a difference?

We have one upstairs and one down.
We also use petal cleanse on the cat.
And buy the new purina live clear food that reduces allergens in saliva of cat.