formication vs itchiness

formication

noun
  • An abnormal skin sensation similar to that of insects crawling over or within the skin; a tactile hallucination involving such a sensation. A common side-effect of substance abuse, it can also be experienced with high fever, menopause, skin cancer, diabetic neuropathy, or herpes zoster. 

itchiness

noun
  • The state of being itchy. 

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