Bunions are an enlargement of the great toe joint of the foot and are commonly associated with what is known as hallux valgus that is a deviation of the big toe towards the outside. They may or may not be painful, though the likelihood of them to be painful is great. For this reason prevention and treatment is usually typically justified. They actually tend to be progressive and become worse with time. Really the only way to get rid of them is with surgery, but that's not always a good alternative at first. One of many ways in which they is often treated is by using what is known as bunion correctors, however they are frequently coupled with the question, will they work? These are splints or braces put on during the night in an attempt to correct the deviation of big toe to improve its appearance.
A lot will depend on what is understood by “working”. There's a lot of thoughts and opinions as to them both working and not working with very little scientific research. There is one published scientific study which did show that the angle of the hallux can be improved by a few degrees after one months use, but this wasn't research of any longer than that one month. So, yes, it does appear that bunion correctors can work in the short term at improving the angle of the hallux valgus or bunion a few degrees.
Apart from that study just about all we can depend upon is expert thoughts and opinions. Most of that opinion is in keeping with that scientific study. However, it also looks like even if the use of the bunion corrector doesn't help the angle of the big toe or hallux or just helps it a tiny amount, it can be feasible that the corrector may go a long way to preventing the problem from becoming worse. That's significant as bunions are progressive. The splint will also be very helpful at stretching the ligaments around the joint which might be helpful with pain within the bunion.