As vinegar in onion helps in many cases.

As corns in apply shredded onion compress, or juice of onion mix in vinegar, boil ten minutes on weak fire, cool, grease for two times/day as a corns.

Or pieces of  onion infuse in vinegar for night, and  apply one to corn, and till a morning,as changing on new on morning, evening as same cure and for heels.