Fleas hate Earl Grey tea. If you open the tea bags and shake them out where the cats sit it discourages fleas.You can also sprinkle it in the carpet and leave for a day or two then hoover up. Salt is also effective used in the same way in the carpet.
Fleas also hate Rosemary.
Boil 2 cups of water add 2 tablespoons of dried Rosemary or I tablespoon of fresh Rosemary to the water and allow to cool.
Once cool strain and pour into a plastic spray bottle.
Spray on to the cat, bedding,carpets and anywhere the cat likes sitting.
Worth a try anyway.
Another natural product fleas hate is lemon.
Slice a lemon,leave peel on, pour one cup of boiling water over the lemon and cut a little slit in the sides of the lemon slices.
Allow to sit overnight.
Dilute with another cup of water and using cotton wool sponge cat with lemon and water solution. You can also spray the cat with this as long as you avoid the eyes and nose.
A cat I once had was allergic to chemicals and I had to use herbal remedies.
Be careful if you use essential oil remedies, they are not really suitable for cats.