Bunions are an enlargement of the great toe or hallux joint of the foot and are frequently related to what is known as hallux valgus which is a deviation of the big toe or hallux towards the outside. They may or may not be painful, however the potential for them to be painful is great. For this reason prevention and treatment is typically indicated. They do tend to be progressive and become worse with time. The only real way to get rid of bunions is with surgery, but that is not necessarily a good alternative in the beginning. One way that they is often treated is by using what is called bunion correctors, but they are often accompanied by the question, can they work? These are splints or braces worn during the night to attempt to correct the deviation of big toe to better its look.
A great deal will depend on what is understood by “working”. There's a lot of opinion as to them both working and not working with not much scientific research. There's one published scientific study that did show that the angle of the hallux will be improved by a few degrees after one months use, however this was not research of any more than that one month. So, yes, it does seem 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 one study all we can depend on is expert thoughts and opinions. Most of that opinion is in keeping with that research study. However, it also seems that even if the use of the bunion corrector doesn't improve the angle of the great toe or only improves it a small amount, it is feasible that the corrector can go a long way to stopping the problem from getting worse. That is important as bunions are progressive. The splint can also be very useful at mobilizing the ligaments surrounding the joint which could be helpful with pain within the joint.