Sudden onset of aggression

I really don't have any answeres for you. I had a male cat that was like that all his life. he was loving and very sweet. But at times just out of the blue he would grab hold of me and bite and dig his claws in me.One time I had to get antibiotics as the bite on my hand became infected. My vet said that some cats studies have shown that are oxygen deprived at birth show this aggresion. Who knows if thats so or not. Just a thought for you though.

He needs major play time and to know his boundries.

I got this from the behavior section of the forum.

First and formost I am assuming that he had a check-up and a clean bill of health. If so try this:

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1. Once the cat attacks, stand perfectly still. Don't try to pull away the hand (or other body part) that she is biting. If you try to pull away, this will trigger the "prey" cues in her brain and she will attack even harder. So, stay still and use your free hand to pull her off.

2. Immediately after an attack, put her in a quiet room (the bathroom) for no more than five minutes. This will give her time to settle down and for attack mode to turn off.

3. Pay careful attention to her behavior. Learn what her pre-attack behaviors are. All cats do something right before attacking, like twitching their tails or their eyes dilate. Each cat has its own unique signals, so you will have to learn your own cat’s signals.

4. Once you have learned her pre-attack signals, IMMEDIATELY upon seeing a signal and BEFORE the attack occurs, do one of the following:
-- toss a small toy in front of her. Toss the toy at an angle across her field of vision but at an angle so that it is going away from her...like the way a mouse would run...toward a wall away from the cat. Cat's brains don't perceive vertical movement very well, so it needs to be tossed across the floor.
-- or use another toy to distract her (never play with her with your hands or feet...always use a toy)
-- or Shout NO!

The main idea is to keep the attack from happening. It won't take too long before she realizes that she can no longer do this.

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Good luck - everything will be fine - he is just getting comfortable and now it time to set the rules.