Bunions are an enlargement of the big toe or hallux joint of the foot and are commonly associated with what is known as hallux valgus that is a deviation of the great toe or hallux towards the outside. They may or may not be painful, though the prospect of them to be painful is great. For this reason prevention and treatment is typically warranted. They do tend to be progressive and become worse over time. Really the only way to get rid of them is with surgery, but that is not necessarily a good solution in the beginning. One way in which they may be treated is by using what is called bunion correctors, but they are often coupled with the question, do they work? These are splints or braces worn at night in an attempt to improve the deviation of big toe to better its appearance.
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 hardly any scientific research. There exists one published study that did show that the angle of the great toe will be improved by a few degrees after one months use, however this was not research of any longer 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 several degrees.
Apart from that one study all we can count on is expert opinion. The majority of that opinion is in keeping with that research study. Nevertheless, it also seems that even if the use of the bunion corrector does not improve the angle of the great toe or hallux or only improves it a smaller amount, it is feasible that the corrector can be quite a distance to stopping the condition from getting worse. That is significant as bunions are progressive. The splint might also be very useful at stretching the ligaments surrounding the joint and that could be useful with pain inside the bunion.