Swollen bottom gums are most commonly caused by gum disease, specifically gingivitis from plaque buildup along the gum line. But several other conditions can target the lower gums in particular, from partially erupted wisdom teeth to hormonal shifts to medication side effects. Identifying the cause matters because some resolve with better brushing habits, while others need professional treatment.
Plaque Buildup and Gum Disease
The single most common reason for swollen gums is plaque, the sticky film of bacteria that accumulates on teeth throughout the day. When plaque sits along the gum line for too long, it irritates the tissue and triggers inflammation. Your gums respond by swelling, turning red, and bleeding easily when you brush or floss. This early stage is called gingivitis, and the lower front teeth are especially prone to it because the salivary glands underneath deposit minerals that harden plaque into tarite faster than in other areas of the mouth.
If gingivitis goes untreated, it can progress to periodontitis, a deeper infection that destroys gum tissue and the bone supporting your teeth. Dentists measure the depth of the gap between your teeth and gums to assess how far things have gone. A depth of 1 to 3 millimeters is normal and healthy. Gaps of 4 to 5 millimeters indicate early gum disease, 5 to 7 millimeters suggest moderate disease, and anything above 7 millimeters points to advanced periodontitis with potential bone loss.
The encouraging part: mild gingivitis typically improves within 10 to 14 days after a professional cleaning combined with consistent brushing and flossing at home. The swelling goes down, the redness fades, and the bleeding stops. More advanced gum disease takes longer and may require deeper cleaning procedures.
Wisdom Teeth and Pericoronitis
If the swelling is concentrated behind your back molars, a partially erupted wisdom tooth is a likely culprit. When a wisdom tooth only breaks partway through the gum, a flap of tissue covers part of the tooth and traps food and bacteria underneath. This leads to a condition called pericoronitis, and it almost always affects the lower jaw because bottom wisdom teeth are more likely to come in at awkward angles.
Chronic pericoronitis causes mild, on-and-off achiness near the back teeth along with bad breath and a persistent bad taste. The acute version is harder to ignore: severe pain around the back teeth, red and swollen gum tissue, pus or drainage, discomfort when swallowing, and sometimes swollen lymph nodes in the neck or even lockjaw. Your dentist will examine the area, check for excess gum tissue, and take X-rays to evaluate the roots and rule out cavities or other problems.
Tooth Abscess
A pocket of infection at the root of a tooth can cause a localized, painful swelling on the gum that sometimes looks like a small bump or pimple. Abscesses in the lower jaw tend to cause swelling along the bottom gum line or even under the chin. You might notice throbbing pain that radiates into the jaw, sensitivity to hot and cold, or a foul taste if the abscess starts to drain on its own.
An abscess won’t resolve without treatment because the infection is trapped. If you develop a fever along with facial swelling, or if you have difficulty breathing or swallowing, that signals the infection may be spreading into the jaw, throat, or neck. That’s a situation that warrants an emergency room visit if you can’t see a dentist right away.
Hormonal Changes
Shifts in estrogen and progesterone can make gum tissue react more aggressively to even small amounts of plaque. These hormones increase blood flow to the gums and change how sensitive the tissue is to bacterial irritation, making gums more prone to swelling, soreness, and bleeding. Pregnancy is the most well-known trigger. Pregnancy gingivitis affects a significant number of expectant mothers, often appearing in the second trimester even in people who previously had healthy gums.
Puberty and menopause can produce similar effects. During puberty, rising hormone levels boost circulation to the gums, and if brushing and flossing habits aren’t solid, the result is noticeable inflammation. In all of these cases, the hormonal shift itself doesn’t cause the swelling directly. It amplifies the body’s inflammatory response to plaque that’s already there, which is why good oral hygiene during these periods is especially important.
Medications That Cause Gum Overgrowth
Certain medications can cause the gums to gradually enlarge, sometimes enough to partially cover the teeth. Three classes of drugs are responsible for the vast majority of cases: anti-seizure medications, blood pressure drugs called calcium channel blockers, and immunosuppressants used after organ transplants.
Among anti-seizure medications, phenytoin is the most common offender. Roughly half of the approximately 2 million people taking it develop some degree of gum overgrowth. Among blood pressure medications, nifedipine carries the highest risk at about 38%, while others in the same class like diltiazem (around 20%) and amlodipine (about 3%) can also contribute. If you’ve recently started one of these medications and notice your gums swelling or growing over your teeth, your doctor may be able to switch you to an alternative.
Oral Appliances and Dentures
Braces, retainers, and dentures can all irritate the gums if they don’t fit correctly or if plaque builds up around them. With braces, bacteria accumulate around the brackets and wires in areas that are harder to clean, leading to localized swelling. Dentures that fit poorly rub against the gum tissue, creating sore spots and chronic inflammation. Lower dentures are particularly prone to fit problems because the lower jaw ridge is narrower and offers less surface area for the denture to grip.
Salivary Gland Stones
Sometimes what looks like swollen gums along the bottom of the mouth is actually a blocked salivary duct. The submandibular glands, located beneath the jaw, drain saliva through ducts that open under the tongue near the lower front teeth. When a small calcium deposit (a salivary stone) blocks one of these ducts, saliva backs up and causes a painful lump under the tongue or along the floor of the mouth. The telltale sign is that the swelling and pain get worse during meals, when the gland produces more saliva and has nowhere to send it.
What You Can Do at Home
A warm saltwater rinse is one of the simplest ways to reduce gum inflammation and keep the area clean while you figure out next steps. Mix 1 teaspoon of salt into 8 ounces of warm water. If your mouth is tender, start with half a teaspoon for the first day or two. Swish for 30 seconds and spit. You can repeat this several times a day, particularly after eating.
Gentle but thorough brushing along the gum line with a soft-bristled toothbrush helps remove the plaque causing the irritation. Many people instinctively avoid brushing swollen gums because they bleed, but skipping the area lets more plaque accumulate and makes the swelling worse. Flossing daily, even if it causes minor bleeding initially, helps clear bacteria from between the teeth where a toothbrush can’t reach. If the swelling is mild and responds to these measures within a week or two, you’re likely dealing with simple gingivitis. Swelling that persists, worsens, or comes with pain, fever, or pus points to something that needs professional evaluation.