Kitten has started biting

 My cat Snickers is 7 months old now and he has just started biting when we try to touch him. He used to be a wonderful kitten and he loved to be cuddled, sometimes he'd get completely obsessed with cuddle time and demand my love and affection all day long. Now a couple of days ago I've seen him bite my boyfriend for no visible reason when he tried to pet him and it was very unexpected since he is such a sweetheart normally. Then a day later he bit me when I touched him and now he goes into full defensive mode almost anytime anyone wants to pet him.

We got him checked by the vet and he has no health issue, he's getting high quality food with 97% protein and he has all he needs including his own cat house where he can hide, elevated sitting sports over the walls so that he can see the rooms from above, cat trees, toys and playtime every day. So I was wondering where that aggressive behaviors could come from and noticed that my boyfriend plays with him pretty roughly using his hands. The cat seems to like playing rough but u can see him snapping at and scratching my boyfriends hands while they play, which he tolerates. So I assume that this must be the source of his aggression. He had simply learned that hands are fine to be attacked.

He won't understand that biting and scratching sometimes can be tolerated and sometimes it's not, so I told my boyfriend to stop playing roughly with him and to not use his hands anymore during playtime. I've thought of rubbing hands my with lemon juice and intentionally seek out a situation where he might bite, without provoking the bite of course. He is not supposed to think that people are bad but rather that biting isn't nice, for him, because cats care most about what's good for them. Then when he does let you pet me without biting I can be really positive about it and show him that I like the way he's behaving. I'd also thought of playing with him as a reward instead of treats. Or make him work for his treats by hiding them inside a toy for example. 

If anyone has any advice for me I'd be grateful  

Has he been neutered yet?  Is he displaying any of the warning signs listed in this article: http://www.thecatsite.com/a/cat-aggression-toward-people?  This article is on Playtime Aggression but may have some useful ideas for you.  And this thread has other ideas on stopping aggression toward people.

You are right to stop playing with him with your hands.  Has anything changed in your home?  Does he go outdoors at all?  Do you have outdoor cats that come near your home?  (Even ones he can't see?)

These are just some of the thoughts/questions that have come to me after reading your post.  Hopefully we can help you figure this out!

I've found that yelling, yes yelling, no or ow when they start biting that it will stop them.  I did that then they were kittens and I still do it now.  It works for me.  And I was consistent with them.

My first thought was the same as @MoochNNoodles  with the neutering question as if not his hormones could well be coming in to play and causing all sorts of confusion and changing his behaviour.  It's good that you have checked things out with the vet and he has a nice clean bill of health at the moment as this would be another concern.  Do keep an eye out for any other changes though as there could be something like sensitive skin or something just starting to bother him but not yet causing noticeable symptoms for the vet to see.  He is probably teething too which won't help!

As you describe your BF playing rough with his hands it could be that Snickers has been learning that this is OK but it seems less likely to me that this would cause a sudden change if BF has been doing this all along.       The other thing to think about is whether something could have happened that could cause Snickers to be more anxious and heighten his responses:  it could be something when you were around or when he was on his own - another animal that might have been around, something he's seen at a window or a loud noise from somewhere.  This kind of thing can result in 'redirected aggression'.

I suggest caution with raising your voice.  A loud or shouting voice can be frightening or seem aggressive and aggravate a stressed cat.  It is usually more effective to use a firm voice which is not too high pitched to say no, or ahah prior to being bitten, or ow, or ouch if you are experiencing pain.  The articles that MoochNNoodles has given you links to give lots more useful advice on how to react and remain still and calm if he is biting and from my experience, while this seems strange and is hard to do, it is definitely the most effective and likely to alter the behaviour - whether it is him confused and trying to play or him feeling threatened and attacking.  Mouse was a very playful and easily over excited kitten / young cat and he was terrible for biting when he was younger.  Stillness, calm, and avoidance of loud noise and fast movement are all your best friends.

2 things I suggest for you.

If you haven't done this already try touching him with something other than your hand, maybe with a wand toy or similar so you can see if he is more sensitive on any particular area of his body while not putting your hand at risk, and also if he reacts in the same way with an object to a hand.  Do this when he is relaxed and not when you have been playing or it would be too confusing for him.  Use the same gentle stroking action that you would with your hand and avoid jerky or fast movements which would seem more like play or aggression to him.

Observe and think carefully about whether his reaction is different depending on which direction you approach him from.  It may be that if you approach from in front this feels more like aggression to him and he could be more likely to strike and defend himself.  Also pay attention to his other body signals like tail position / movement, ear position, and eyes.  These can all show whether Snickers is more relaxed or tensed and ready for defensive action.

I really hope this is a short term behaviour with Snickers and you are able to figure out what has caused this change.  Most likely will be hormones if not neutered I think.   

  First question would be has he been neutered. As previously stated the hormonal shift when they go into puberty is overwhelming physically and mentally.

Males instinctually will bite and pin down their partner and at young age they will practice this on just about anything.

    If he hasn't been neutered yet, I recommend you do so ASAP.

    Please keep us updated