The short answer is yes, glass sex toys are safe to use for their designed purpose. You need to use a glass sex toy with a flared base for anal stimulation. Purchase your glass sex toys from a reputable, trusted company, and buy well-known tried and tested brands for reassurance of safety and quality.
What are glass sex toys made from? Obviously glass - but this type of glass feels different to how many people imagine. Instead of being fragile and easy to shatter (such as window panes), glass sex toys are made with borosilicate glass. They are also solid sculptures rather than hollow. This makes them heavier to hold and shatter resistant. Borosilicate glass is the same type of glass used for oven dishes and other bakeware. The best known brand is Pyrex. That should give you a clearer idea about just how long lasting and damage resistant glass sex toys are.
Glass is the sex toy material of choice for pleasure product connoisseurs around the world. Not only are many glass sex toys so beautiful that they could double as ornaments, they are also non-porous making them easy to keep clean between uses. Glass sex toys are compatible with any type of sexual lubricant too. You can simply grab your favorite bottle and slip and slide without worrying about damaging your toy. If you're still unsure about glass sex toys, it might be worth asking your nearest sex shop if they have any glass sex toy samples you could check out. This will give you a better idea about the material and cure some common fears. There are glass sex toys designed to suit the majority of stimulation preferences: butt plugs, vaginal dildos, and vaginal vibrators; there is also a choice between smooth, ridged, and noduled styles.
You can read more about the safety of glass sex toys and commonly held myths in my article.