PrettyLitter and other silica gel crystal litters are safe and non-toxic for cats. The silica gel found in most of these cat litters is also used in moisture-absorbing packets placed in medications, new shoes, and other products.
Vets seem to consider crystal litter as safe. The lack of dust, as opposed to clay litters, can reduce health risks for cats and humans, particularly those with asthma or dust allergies. And crystal litters are less likely to grow bacteria or mold.
A potential hazard has been concerns of cats eating the crystals. While they should pass through their digestive system without issues, kittens may be tempted to ingest too many and should be monitored.
In addition, older cats may eat the silica gel crystal litter if they have feline pica, a health condition that causes cats to eat inedible things. Feline pica can be due to mineral deficiency or psychological disorders. Again, be sure to monitor your cat's bathroom behaviors if switching to silica crystals like PrettyLitter.