I bought these for my son. I was looking for some fun bath time things since the same toys over and over can get boring. I had never stopped to think about our bath tub. It says on the container that it "could stain porous surfaces" our bath tub is an older claw foot where the lower surface has worn away. So I didn't want to take the chance of having a red or blue bath tub, I decided to let him play with them in the sink. They change the color of the water quickly and it is bright. It washes away from the surface of out sink and from skin easily. I wouldn't let this get on clothing. He was splashing too much so I picked up the drop that was still dissolving to throw it away and it felt like it was burning my fingers. It didn't burn me but it did cut my finger open! And it was bleeding pretty good. I can't imagine my son grabbing a hold of one of these and what it would do to his tiny fingers. I just wanted to put this review on here as a precaution to parents who buy these with smaller children let it dissolve before they get in the tub or just be extra careful. It says three and up on the tub but I would go as far as saying probably older than 5 or 6 and up.