is vinegar poisonous to cats?

I rubbed vinegar on my kittens for fleas but the mamma cat licks it all off. Then i heard that cats should not ingest vinegar as its poisonous to them if they drink it. Should i stop rubbing them with vinegar? I don't want mamma cat to get sick. Would it be safer to rub lemon juice on them instead to repel fleas?

I would not put vinegar or lemon juice on the kittens. They are both irritants to the skin and mucous membranes (eyes, nose, mouth). The acidity alone could cause skin sores, an upset stomach, acid indigestion, vomiting, and interference with urine pH.

There was a thread that got revived recently:

http://www.thecatsite.com/t/246382/apple-cider-vinegar-and-cats

Personally, I would only use apple cider vinegar, and externally. If mama licks it, then I wouldn't use it. But others in the above thread had different results.

Apple Cider Vinegar would be a much milder form of vinegar to use for this purpose. White vinegar is much too harsh. While apple cider vinegar is not poisonous to cats, you should always be using a dilute mixture, never full strength.

To make a spray, you can mix 1 cup ACV to 1 cup of water into a spray bottle and spray this on your hands and then apply to your cat's coat. Never spray this around your cat's face, but use your hands to apply to the neck area in a downward motion, or you can spray a cloth and then wipe carefully around the top of the head, backs of the ears, throat, etc. 

All great advise. Thanks so much. Anyone know any more about diluted lemon juice? What do you think would be the best method for kittens Approx a month and a half old.

Citris scents are used as a cat repellent, so I would not use lemons or oranges.