Why Gums Swell

Swollen gums are relatively common, but can signal an underlying health problem.
list of possible causes:

Having an inflamed gum condition called gingivitis.
Having a fungal or viral infection.
Being malnourished.
Wearing dentures that don't fit properly.
Being pregnant.
Being sensitive to a mouthwash or toothpaste.
Having scurvy.
Experiencing a side effect of certain medications.