Gingivitis is caused by the buildup of bacterial plaque on your teeth, which triggers an inflammatory response in the surrounding gum tissue. Nearly half of adults over 30 have some form of gum disease, and gingivitis is the earliest, most reversible stage. While plaque is the primary driver, several other factors, from hormones to smoking to nutritional gaps, can accelerate or worsen the condition.
How Plaque Triggers Inflammation
A thin layer of bacteria begins colonizing your teeth within hours of brushing. The first to arrive are relatively harmless species like streptococci and actinomyces, which attach to the protein film that naturally coats your enamel. These early settlers create a foundation for more problematic bacteria to latch onto, including oxygen-avoiding species that thrive in the tight crevice between your teeth and gums.
Your immune system responds to this bacterial buildup by sending white blood cells called neutrophils through your gum tissue and into that crevice. In a healthy mouth, this is actually a good thing. The neutrophils create a low-level protective inflammatory response that helps maintain the right balance of bacteria and keeps harmful species from taking over. The goal of brushing and flossing isn’t to sterilize your mouth. It’s to reset the bacterial population so the helpful species recolonize the tooth surface and work with your immune system to keep unwanted bacteria out.
Problems start when plaque is left undisturbed for too long. The bacterial community matures, and more aggressive species move in. These include organisms that produce toxins and enzymes capable of irritating gum tissue directly. Your body ramps up inflammation in response, sending more blood to the area, which is why inflamed gums look red, feel swollen, and bleed easily when you brush or floss. At this stage, the inflammation itself starts doing damage to your own tissue.
Hormonal Changes and Gum Sensitivity
Pregnancy is one of the clearest examples of how hormones affect gum health. Rising levels of estrogen and progesterone during pregnancy increase blood flow to the gums, make the tissue more sensitive to plaque, and can change the size and shape of the gums. By the third trimester, progesterone levels are roughly 10 times higher than during a normal menstrual cycle, and estrogen levels are about 30 times higher. Gum tissue contains receptors for both hormones, which means the tissue responds directly to these surges.
The result is that even a normal amount of plaque can provoke a much stronger inflammatory reaction. Pregnancy gingivitis is common enough that it’s considered a distinct condition, though it operates on the same basic mechanism: bacteria plus an exaggerated immune response equals inflamed gums. Puberty creates a similar dynamic on a smaller scale, as does the hormonal shift around menstruation.
Diabetes and Blood Sugar
Uncontrolled diabetes creates a two-pronged problem for your gums. High blood sugar weakens white blood cells, reducing your body’s ability to fight infections. At the same time, elevated sugar in your saliva feeds the bacteria in plaque, accelerating their growth. The CDC notes that diabetes can increase harmful bacteria in the mouth, make gum disease more severe, and slow healing significantly. Infections that would resolve in days for a healthy person can linger for weeks in someone with poorly managed blood sugar.
How Smoking Masks the Warning Signs
Smoking has a paradoxical effect on gingivitis. Nicotine constricts blood vessels in gum tissue, which reduces blood flow to the area. This means smokers often have less visible bleeding and less obvious redness, the two symptoms most people rely on to notice gum problems. Studies comparing heavy smokers to non-smokers consistently find that smokers show lower scores on gum bleeding indexes despite having worse overall periodontal health, with deeper pockets around their teeth and more tissue attachment loss.
In other words, smoking doesn’t protect your gums. It hides the evidence of damage while the disease progresses underneath. Heavy smokers are particularly vulnerable to missing the early signs of gingivitis entirely, which means the condition is more likely to advance to periodontitis before it’s caught.
Vitamin C Deficiency
Vitamin C plays a central role in building and repairing connective tissue, including the tissue that holds your teeth in place. When intake drops low enough, the gums become swollen, spongy, and prone to bleeding, a hallmark of scurvy. In severe cases, the gums turn purple and teeth loosen or fall out. Even moderate deficiency can weaken gum tissue enough to make it more susceptible to plaque-driven inflammation. Dental and gum damage from prolonged vitamin C deficiency can take weeks to months to resolve, and severe gum disease from this cause may leave permanent damage.
Medications That Affect Gum Tissue
Certain prescription drugs can cause gum overgrowth, a condition where the tissue between teeth becomes enlarged and creates deeper pockets where bacteria accumulate. The most common culprits are anti-seizure medications (particularly phenytoin), drugs used to suppress the immune system after organ transplants, and some blood pressure medications in the calcium channel blocker class. The overgrown tissue itself isn’t infected, but it creates an environment where plaque builds up more easily and is harder to clean away, setting the stage for gingivitis.
Medications that reduce saliva production also contribute indirectly. Saliva helps wash bacteria off tooth surfaces and neutralizes acids in the mouth. Hundreds of common medications list dry mouth as a side effect, including antidepressants, antihistamines, and certain blood pressure drugs. Chronic dry mouth shifts the bacterial balance in favor of species that cause gum disease.
Non-Plaque Causes
A small category of gingivitis has nothing to do with oral hygiene. Viral infections, particularly oral herpes simplex, can cause painful gum inflammation that looks similar to plaque-induced gingivitis but requires different treatment. Fungal infections, including oral candidiasis, can also affect gum tissue, especially in people with weakened immune systems. These non-plaque gingival diseases are far less common but worth recognizing because they won’t respond to brushing and flossing alone.
Why Some People Are More Susceptible
The same amount of plaque doesn’t produce the same degree of gingivitis in every person. Your individual immune response plays a major role. Some people mount a more aggressive inflammatory reaction to the same bacterial load, which means their gums become red and swollen faster. Genetics influence this response, as do stress levels, sleep quality, and overall nutritional status. Age is also a factor: the immune system becomes less precise over time, which partly explains why the prevalence of gum disease climbs steadily after age 30.
Crowded or misaligned teeth, poorly fitting dental restorations, and orthodontic appliances all create areas where plaque accumulates more easily and is harder to remove. These aren’t direct causes of gingivitis, but they raise the baseline difficulty of keeping your mouth clean enough to prevent it. The underlying equation remains the same: bacteria that aren’t regularly disrupted will trigger an inflammatory response in your gums, and anything that tips the balance toward more bacteria or a stronger inflammatory reaction increases your risk.