"Is it safe to let a dough made with warm milk and yeast rise at room temperature for an hour and a half, or will the milk go bad and make us sick?"
My source for all the “why’s” behind good food safety practices, Donald Schaffner, Food Science and Professor at Rutgers University and podcaster at foodsafetytalk.com explains, “When we mix yeast with warm milk and let the dough rise at room temperature for 1-2 hours, we are deliberately causing “spoilage” by a desirable organism—yeast.” He likens the process to making yogurt from milk by “spoiling” it with lactic acid.
So, to answer your question:Yes, it is safe. No worries.
Recipe: Cinnamon-Bun Bread