Gingivitis is a disease of the gums, a milder form of periodontal disease. Gingivitis is often caused by inadequate oral hygiene, which leads to plaque buildup. Other factors that may contribute to gingivitis include diabetes, smoking, aging, stress, inadequate nutrition, puberty, hormonal fluctuations, pregnancy, substance abuse, HIV infection, and certain medication use. The bacteria in dental plaques irritate the gums and cause infection. When your body launches an immune response against these invaders, the gums become inflamed. People with gingivitis usually experience little or no discomfort. Therefore, it is important to recognize the symptoms, such as gums that are red, swollen or bleed easily.