The information provided here is not a replacement for a doctor. You shouldn't use it for the purpose of self-diagnosing or self-medicating but rather so you can have a more informed discussion with a professional TCM practitioner.
Because it is a herb specifically indicated to treat inflammation of the lungs as can be seen on Snake Gourd Root's page.
Its main actions are: Clears Heat in the Lungs and moistens Dryness, especially when there is Phlegm that is aggravating the condition. Brings down inflammation and reduces pus.