Chilblains are a relatively common lesion on the toes of the feet in colder climates. They start as a red itchy painful lesions that progresses to a chronic dark blue lesion.

Curated Resources:
https://croydonfoot.com/chilblains-season-is-here/
https://www.itsafootcaptain.com/beetroot-juice-for-chilblains-say-what/
http://podchatlive.com/episode-80-chilblains/
https://thescienceandmyopinion.com/chilblains-the-science-and-my-opinion/
http://podiatryarena.com/index.php?tags/chilblains/
https://podiapaedia.org/wiki/peripheral-vascular-disease/chilblains/
https://www.footstore.com.au/browse-for-products-by-condition/chilblains/
http://www.podiatryexperts.net/question/89/Anyone-got-some-advice-for-chilblains