In reply to Liamhutch89:
This happened to me about 15 years ago with a pair of Scarpa shoes (forget the model, no longer made but they were pink unlined leather)
Like you, I'd worn them for a few months before it happened, I didn't go to a doctor, just stopped wearing the shoes which are still in a cupboard somewhere at home.
I've never had a problem with any other shoes before or since.