Young kitten..is diarhea dangerous?

My new kitten, Luna (2 months), has been having diarhea for two days now. The strange thing is, it was not two days straight, she mad one perfectly normal poop yesterday, but it was more gooey and yellowish yesterday night and this morning.
She acts perfectly normal, drinks and eats enough, plays around, is very vocal. But I recently had to change her kitty-food from Science Diet for kitten to Royal Canin because she wouldn't eat SD anymore. Can this be the cause?
Or can it be stress caused by her brother Timine (3 months), he's way bigger then her and constantly wants to "play".

how recently did you change the food? and did you change it over all at once or did you introduce her to it slowly?

Its quite common for this to happen when you change their food - however I would be keeping good eye on her - diarhea can be dangerous if it continues for too long

Danielle is right in what she's said. When you change a brand of food over it's best to mix some of the new food in with what their eating already to get it used to their tummies because kittens tummies especially are sensitive.

But yes keep an eye on her and make sure she drinks her water ok

Most food-change induced diarrhea comes from a change in wet food, not dry food, or an overly rich food including kitten foods. But in an 8 week old kitten diarrhea can be very dangerous and you have to assume its either worms or a parasite. All kittens should be de wormed, twice, two weeks apart, the first time around the age of your kitten.

I would also highly recommend a stool sample be tested for parasite because common parasite borne illnesses like coccidia (very common in kittens especially rescued or shelter kittens) can be fatal if untreated as in time the wall of the intestine will be destroyed. Treatment is an easily administered liquid.

Your worst fear if for the kitty to become dehydrated. If you lightly scruff the neck of the kitten while it is on the ground, and then release, the skin should not stay tented up at all.It should fold down to normal in seconds. If it stays pinched up get the kitten to the vet immediately- because it needs more fluids than you will be able to give it. If the diarrhea continues get her to the vet as well, or at least a stool sample so it can be tested.

Thank you all!
I've read a bit around the board, and yes, I'm checking on her water intake.
I'll still try the pinching the neck trick and be very attentive.
I changed her food two days ago, and I wanted to mix it with her old food, but she wouldn't touch it. So maybe it's the drastic food change. If it is, will the diarhea go away on it's own? The food is suppossed to be very good for kitten's sensitive tummies.
I sure hope it isn't worms or this kind of stuff...she is from a pet-shop, not a shelter, but I read that those places can be just as dangerous...
Now I'm worried...if it isn't better tonight, I'll bring her to the vet.

Updates on Luna...
She got the the Vet Friday night, and they said their were no worms or parasites of any kind. Still, they gave me little pills and she has to take one every months. (The horror of doing that!!! But it's for her good!)
They also told me to mix white rice with it's boiling water (cooled, yes..) to her food to clear out the diarrhea. I did, and was very surprised to see that Luna loves rice, even on it's own.
The problem is, it hasn't changed a thing! Not even slightly. Now what should I do? I heard pumpkin is good for that? She's been a whole week on Royal Canin...is it too late to switch back to the Nutrience they gave them at the Pet-Shop? Maybe it's something in Royal Canin...although I know it IS better then Nutrience...

Pumkin is for constipation so it would be the exactly wrong thing to give her. If her diarrhea is being caused by upset bowels, you could try the well respected technique of fasting her for 2 days, and then introducing a very gentle food, chicken and rice, or baby food stage 1. You can discuss this with your vet and research the fasting technique online.

Yes. don't arbitrarily pull all her food for two days, there is a procedure to follow and you do give liquids, but talk to your vet. Did they test for coccidia, giardia, all those? Or do you know? If you do switch food, switch it slowly. One tablespoon per day of the good stuff, mixed with the regular food, over a week increase the new food. It could just be her gut has bad bacteria in it. You can either go with GSE (grapefruit seed extract) 2 drops in her food every time you feed, or you can get some acidophilus capsules and sprinkle the powder over her food (canned food) and mix it in well. Failing that, plain yogurt with active cultures will also help her. But first call the vet and ask what they screened for- just worms?

Once again thank you!
I got many suggestions and got to the grocery store yesterday night wondering what I would pick up...
I finally chose the simple option and bought chicken baby-food and plain yogourt with active things in it.lol Can't remember the term, sorry.
Well, Luna didn't care much for the yogourt, but she loved the chicken mixed with good ol' rice.
And good news! I found a nice little poo in her litter box this morning. I've never been so happy to see a semi-formed cat-poo in my life!
Now all I will have to do is slowly reintroduce Royal-Canin in her diet...sloooowly.

Luna got better after a few meals of baby food and rice, so I decided to re-introduce her usual kitten food a little bit at a time. But now everytime I put even a bit of the food into her rice, she starts having soft poop again. Is it normal...will it adjust?

I always tell folks switching cat food especially kittens and senior it can be a three week process...

Ok, it just worries me, she needs real food to grow up!

ARG!!!
Not so good update! Will this ever end!?
So I was resolute to let Luna grow accustomed to her food gradualy, but yesterday her "brother" Timine (3 months+) started to have mushy stools too!
Now I went to the vet with Luna two weeks ago and she isn't suppossed to have any bacterias, she even got pills to take every month!....and when I give her only rice and chicken, she gets better, so I assumed it was only a digestion problem...what's wrong? Why is Timine sick now?!