The cat could possibly be biting because they are hurt or injured in some way and they are in a defensive mode.
Another reason is if they are scared of something such as a dog which again put them in a defensive mode.
It may be strange but they could also bite because they have re-directed their anger onto you.
An example of this is when another feline is outside and they can see them through the window and as soon as you open the door they could swipe at you instead.
So how do you stop the cat from biting you? You can actually buy pheromones spray which emits a friendly smell into the air.
Any brands of kitty pheromones work however I would recommend using feliway comfort zone as I am using this product.
This will ultimately calm them down and can be used in a variety of ways such as calming them down to go to the vets.
You should never play with your pet with their toys in your hand because they may associate your fingers with things to attack and bite.
What you should do is get a fishing rod toy so that your hands are well away so they will never associate you with prey.
If you do get bitten then you should never pull away because they will only bite harder.
Instead you should scream "ouch" in a high pitched noise and push your fingers towards their mouth.
Ultimately they will release you as prey will never act this way.
You should also cease playing with them for ten minutes and ignore them so they get the message.