pustule vs wheal

pustule

noun
  • A pimple filled with pus. 

  • A small accumulation of pus in the epidermis or dermis. 

  • Anything like a pustule, on plants or animals; a small blister. 

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 pustule and wheal occurred in a corpus of books? (source: Google Ngram Viewer )