Reiterating what we said above, what precisely causes a bunion is uncertain but diagnoses point towards certain foot types that make for the perfect conditions for bunions to form.
However, since those foot types run in families, bunions can be called a hereditary issue. It’s important to remember though that certain lifestyle practices like wearing ill-fitting shoes or standing for long hours may contribute to the issue as well.
To avoid forming bunions on the side of the foot, wear shoes that fit you well, that are made of soft materials, and that won’t chafe against your skin.