The first 24 hours were fine except they were very hard to get out. This got better over time. But very soon I developed a funny dry cough. I didn't feel like I was getting sick, just had a persistent cough. It grew worse over a couple days and I began to suspect the new clear braces. I realized that I stopped coughing soon after taking them out! I googled "Invisalign Allergic Reaction" and got several hits. Others had the same problem, some accompanied by nausea. Yikes! My new plan to correct my bite has hit a wall! My ortho never heard of this, but I cited the pages on-line. He is currently contacting his Invisalign rep and will get back to me. Waaah! I don't wanna be a metal mouth again at this age!