ulcer vs wheal

ulcer

noun
  • An open sore of the skin, eyes or mucous membrane, often caused by an initial abrasion and generally maintained by an inflammation and/or an infection. 

  • Peptic ulcer. 

  • Anything that festers and corrupts like an open sore; a vice in character. 

wheal

noun
  • A small raised swelling on the skin, often itchy, caused by a blow from a whip or an insect bite etc. 

  • A mine. 

verb
  • Synonym of wale. 

How often have the words ulcer and wheal occurred in a corpus of books? (source: Google Ngram Viewer )