Slime is as safe as you make it. If you decide to buy your slime, check the ingredients and ensure that you're buying from a trustworthy retailer. Some slimes have been labelled toxic because they contained a worrying amount of boron.
You can lower the risks of danger by taking a couple of simple steps. If you're worried that the slime may get eaten, you might want to make an edible variation. If you're working with ingredients like laundry detergent, be sure to take appropriate precautions such as hand washing.