It really depends on the type of glue. I'm not sure whats in glue gun sticks so I can't tell you whether its safe or not. The three top glue choices are silicone, epoxy, and crazy glue with silicone being the best, IMO, choice you have. Be sure that it is pure silicone and not mildew resistant like tub and tile silicone. Door and Window silicone is usually the one to go with but read the labels and they will say if its got additives.