What Causes Chilblains On Toes?

I am convinced right now that that the itchy blistery lesions on my all my toes are Chilblains. They are turning black-blue color now, I had something similar happen at the edges of my nostrils. Thought it was because of using dry wipes when I had a cold. I have recently been diagnosed with hyperthyroid, which doc thinks might be incidental (two CT scans in four days - iodine used). Could there be a link between the thyroid antibodies and chilblains? Never had them before.