Some cats are more sensitive than others to flea bites. They can have reactions to the flea saliva which causes intense itching that will make their lives miserable.
Sensitivity to fleas is quite common. You may notice your cat has pink to red skin and hair loss through overgrooming. There can also be small red crusts and bumps on the back and rump.
Only complete eradication of the all the flea life stages will protect your cat from a sensitivity to fleas.
Flea video VECTRA 3D