Yes, crystal dildos are made from body-safe, hypoallergenic materials.
Wash with warm water and mild soap, and make sure that the item is dehydrated.
Yes, they can always be warmed or cooled to intensify the feelings.
They are quite long-lasting, but one has to be very careful not to damage one by dropping it or applying too much force.
These are elegant, hypoallergenic, and able to retain temperature.