Is it normal for cats to suckle human nipples? I have had this cat for about 3yrs now, and I can’t sit on the couch without a shirt on, for fear of the nipple sucker.
laugh
That is pretty normal for a cat who wasn’t weaned properly when it was a kitten. It might have been taken from it’s mother at too young an age. Cats that do this usually also suck on things like wool, or fingers, or anything else that reminds them of “mom”. It’s pretty hard to break a grown cat of this habit, and I don’t suggest you try. It would be hard on the cat, and you, assuming you like your cat. 
Wow, so I’m not the only one…I now avoid lounging topless when my cat might have access.
Yeah. Wow, so lots of cats do that, apparently. I used to date a guy whose cat did that. (Mostly the cat went for my nipples, I assume because they stuck out more.) It was kind of a problem, because I am really allergic to cat spit —I get red weeping welts that last for hours— and having itchy nipples, especially in public, is a bit awkward.
He was a nice kitty cat though.
I must say that a thread like this warrants no response from me at all
After Pepper Mill took a shower one time one of our cats was standing on the sink, licking beads of water off of her as she toweled down. Just as the cat got to Pepper’s nipple, she bit it. Gently – more a trial nibble or love bite than anything else. Pepper was more surprised than hurt. It hasn’t happened since.
None of the other cats has shown a propensity for this. Good thing, too. I’m highly territorial.