I rescued two kittens, a brother and sister, around the beginning of August when they were about 6 weeks old. They are now about 10 weeks old I’d say and nothing has gone wrong with them until now.
The other night, I bought some Pounce cat treats and some catnip for a new scratching post, along with a catnip toy. They seemed to LOVE the treats, and played with the toy all night long and even began to use the scratching post. But later that night, they started to throw up this clear, frothy like liquid.
The next morning I noticed they hadn’t ate overnight or gone poop, but had continued to pee. I watched them all morning and they started to throw up the clear stuff again. They would walk to their litter box, meow a few times like they were in pain, I would get a paper towel to put under them and then they would throw up clear or yellowish liquid. The weird thing is, they would run away and start hopping around and wrestling with each other.
Yesterday I bought some Fancy Feast which they took a liking too, they’ve been slowly drinking water, I even noticed poop in the litter box again, and with their energy level just as high as always I figured they must be getting better.
But this morning my fluffy baby just puked some more bile i guess, and as I watched him, something long and white was hanging from his mouth, and then he just swallowed it back up.
Could they have been having an allergic reaction to the Pounce or Catnip, since they were fine until they encountered these? Also I’m worried that what I saw was his tapeworm coming out of his mouth. I have ordered tablets for worms that should be here in a few days, along with Revolution.
Has anyone had this happen to them that can shine a little light and ease a little stress? 
And Fancy feast was only added to their diet after they began throwing up since they wouldn’t touch their dry food.
Well first off all, yes, they are on Purina kitten formula food.
When I called the local vet, they told me that kittens sometime do this and I should bring them in if they energy level decreases and if they cease to eat and drink completely.
Fancy Feast is the only canned food I have gotten a positive response with.. A couple other brands they would turn their nose to
*another edit* lol.
The deworm tablets I am ordering are the exact same thing they will give them in office: Drontal. They let me know I can order from 1800 Pet Meds, which helps me not have to pay for the office visit + exam and testing fees at their office. It’s for sure tapeworms because they have those little dried seed like things where they sleep.