Orthotics are meant to prevent foot problems and help your shoes fit better. So, if you are developing blisters while wearing orthotics, then something is definitely wrong. Here's a look at some of the most common issues that can lead to blisters when wearing orthotics — and what you can do about them. Your orthotics are too large for your shoes. Most orthotics, at least those that you buy over the counter, are made to be trimmed to fit your shoes.