Swollen gums are almost always a sign of inflammation, and the most common trigger is bacterial buildup along the gumline. About 42% of American adults over 30 have some form of gum disease, making it the single most likely explanation. But bacteria aren’t the only cause. Hormonal shifts, medications, nutritional gaps, allergic reactions to dental products, and even poorly fitting dental work can all make your gums puff up.
Plaque Buildup and Early Gum Disease
The most frequent reason for swollen gums is gingivitis, the earliest stage of gum disease. When plaque (a sticky film of bacteria) sits on your teeth and along the gumline, it irritates the surrounding tissue. Your immune system responds with inflammation: redness, puffiness, and bleeding when you brush or floss. Gingivitis is reversible with consistent oral hygiene and a professional cleaning, and it typically causes no permanent damage.
Left untreated, gingivitis can progress to periodontitis, a more serious condition where the inflammation starts breaking down the gum tissue and bone that hold your teeth in place. As gums deteriorate, they pull away from the teeth and form gaps called pockets. Bacteria settle into those pockets, driving a cycle of deeper infection and more tissue loss. Nearly 60% of adults 65 and older have periodontitis. Unlike gingivitis, the bone loss from periodontitis is not reversible, though treatment can stop it from getting worse.
Certain mouth bacteria are especially destructive. One species in particular has evolved ways to hijack your immune system’s signaling, essentially turning off the very defenses meant to kill it. This lets the bacteria survive longer, recruit more harmful species, and amplify inflammation in the surrounding tissue. The result is chronic swelling that won’t resolve on its own.
Hormonal Changes
Pregnancy is one of the most well-known hormonal triggers for gum swelling. Rising levels of estrogen and progesterone increase blood flow to gum tissue, making it more sensitive to even small amounts of plaque. The gums can change in size and shape, and inflammation that might have been minor before pregnancy becomes visibly worse. By the third trimester, progesterone levels are roughly 10 times higher and estrogen levels about 30 times higher than during a normal menstrual cycle, which is why swelling often peaks late in pregnancy.
Gum tissue contains receptors for both estrogen and progesterone, so it responds directly to fluctuations in these hormones. This means puberty, menstruation, and menopause can also cause temporary gum swelling or tenderness, even when oral hygiene hasn’t changed. If your gums seem to flare up on a predictable cycle, hormones are a likely factor.
Medications That Cause Gum Overgrowth
Several common drug classes can cause the gums to physically enlarge, a condition called gingival overgrowth. The three main categories are seizure medications, blood pressure drugs, and immune-suppressing medications used after organ transplants. Despite working in completely different ways in the body, all three share this side effect.
The numbers vary by drug. Among people taking phenytoin (a widely prescribed seizure medication), roughly half develop some degree of gum overgrowth. Nifedipine, a blood pressure medication, causes it in about 38% of users. Other blood pressure medications in the same class have lower rates: around 20% for diltiazem and 3 to 19% for verapamil and amlodipine. Cyclosporine, used to prevent organ rejection, carries reported rates anywhere from 13 to 85%.
If you’ve recently started a new medication and noticed your gums swelling, it’s worth checking whether it falls into one of these categories. Your prescriber can often switch you to an alternative.
Vitamin C Deficiency
Vitamin C is essential for building and repairing connective tissue throughout your body, including the tissue that supports your teeth and gums. Without enough of it, your gums can swell, bleed easily, and become spongy. Severe deficiency leads to scurvy, which is rare in developed countries but still occurs in people with very restricted diets, certain eating disorders, or conditions that impair nutrient absorption.
You don’t need to reach full-blown scurvy for low vitamin C to affect your gums. Even moderate insufficiency can weaken the collagen structure that keeps gum tissue firm. A blood test can confirm your levels if dietary intake is a concern.
Reactions to Dental Products
Your toothpaste could be the culprit. A survey of 289 toothpastes sold in the UK found that 99% contained fragrances, and many of those fragrance compounds are known allergens. Limonene (a citrus-derived ingredient) appeared in 55% of products. Menthol-related compounds showed up in over a third. Ingredients like eugenol, cinnamal, and cinnamon oil have all been linked to allergic reactions in the mouth.
Sodium lauryl sulfate (SLS), the foaming agent in most toothpastes, is present in about 55% of products and acts primarily as an irritant rather than a true allergen. It has been associated with burning mouth symptoms and, in rare cases, allergic reactions. Tin-based fluoride compounds, used for their antibacterial properties, have also recently been connected to allergic inflammation of the lips and gums.
If your gum swelling started after switching toothpaste or mouthwash, try a product free of SLS and artificial flavoring for a few weeks. Improvement within that window strongly suggests a product reaction.
Poorly Fitting Dental Work and Misaligned Teeth
Braces, dentures, crowns, and bridges that don’t fit properly create constant mechanical irritation against the gums. They also create hard-to-clean areas where plaque accumulates, compounding the problem. Crooked or crowded teeth do the same thing by forming tight overlaps that are nearly impossible to floss effectively.
Untreated bite misalignment doesn’t just cause localized swelling. Over time, it can lead to gum recession and increased risk of decay in the spots where cleaning is most difficult. If swelling is concentrated around a specific restoration or appliance, the fit likely needs to be adjusted.
What a Dental Cleaning Involves
For gingivitis and mild gum disease, a standard professional cleaning is usually enough. For deeper pockets, a procedure called scaling and root planing goes below the gumline to remove hardened plaque (tarite) and smooth the root surfaces so gums can reattach. Most people return to normal activities the same day, though the gums may feel sore for a couple of days afterward.
The procedure is typically done in one or two visits, sometimes with a local anesthetic to keep you comfortable. Improvement in swelling and bleeding usually becomes noticeable within a week or two, with continued gains over the following months as long as daily brushing and flossing stay consistent.
Signs That Need Immediate Attention
Most gum swelling is not an emergency, but certain combinations of symptoms signal a potentially dangerous infection. A fever paired with facial swelling suggests the infection may be spreading beyond the gum tissue into the jaw or neck. Difficulty breathing or swallowing is the most urgent red flag, indicating the infection could be compressing your airway. If you experience either of these and can’t reach a dentist, go to an emergency room.