Chilblains
Chilblains area common problem in some countries and unheard of in others. They tend to commonly occur in colder climates.
Once they occur, it is important to keep the foot warm (link to advice) and prevent it from happening again. There is not a lot of research done on them despite how common they are (link to the research). They are more common in females, so that suggest hormonal issues, but the do occur in males. Lots of questions gets asked in forums and often the answers for a “cure” are just not there, so a lot more research is needed to get to the bottom of this small, but annoying problem.