Not all itching and scratching is due to fleas. Try running a fine toothed comb through its fur. If you find what appears to be 'pepper', this is flea dirt, a gentile way of saying flea poop.
Cats can also itch because of inhaled, contact or food allergies.
Cortisone and antihistamines are commonly used to control the signs. There are holistic, complimentary alternatives. Vitamins supplements with high levels of A,C and E have shown promise in optimizing the immune system. Health blends of live plant based enzyme are available. If you suspect that your pet may have a food allergy, simply changing from one brand to another is not the answer.