How can you tell the difference between thrush and just milk stain on the tongue of a 1 month old?

Thrush vs. milk: Sometimes it can be challenging to tell the difference between early thrush and retained milk on the tongue. Generally, milk will wipe away when gently scraped, but thrush will not. Thrush on the tongue will generally spread to the inner cheeks, gums and roof of mouth if untreated. Rapid progression of white patches is suggestive of thrush.