A gum that swells is your body sending in reinforcements. The rush of blood and immune cells makes the tissue puff up — that's the normal mechanism of inflammation. The question is what it's defending against, because the answer completely changes what you should do. Here are the seven most common causes, and how to recognise them.
1. Dental plaque (by far the number one cause)
In eight cases out of ten, diffuse swelling along the teeth points to a build-up of plaque at the neck of the tooth. The swelling is even, affects several teeth, and comes with redness and bleeding when you brush.
What helps: going back to gentle but methodical brushing twice a day, and above all cleaning between your teeth every day. The improvement is visible within a week.
2. Tartar below the gum line
When plaque stays put, it mineralises and becomes tartar — hard, rough, impossible to remove with a brush. If it forms below the gum margin, it keeps up a permanent inflammation that your routine won't fix.
What helps: a scaling at the dentist, and nothing else. If your gum stays swollen despite three weeks of an impeccable routine, this is very probably it.
3. A trapped piece of food
A popcorn kernel, a fish bone, a piece of nutshell slipped under the gum: the swelling is very localised, often painful, and appears suddenly after a meal.
What helps: careful flossing or a jet from a water flosser. If the foreign body doesn't come out within 48 hours, see a professional — the risk of an abscess is real.
4. Brushing too aggressively
Paradoxical but common: scrubbing hard with stiff bristles mechanically irritates the gum, which swells and eventually recedes. The swelling concentrates on the areas you brush most energetically, often on the side opposite your dominant hand.
What helps: switching to soft bristles, holding the brush with three fingers like a pen, and favouring small circles over horizontal back-and-forth strokes.
A simple giveaway: if your brush bristles splay out within less than two months, you're pressing too hard.
5. Hormonal changes
Pregnancy, puberty, the menstrual cycle, contraception: oestrogen and progesterone increase the gum's reactivity to plaque. In pregnant women this is known as pregnancy gingivitis, which affects up to half of all pregnancies, generally from the second trimester onwards.
What helps: stepping up your hygiene during these periods, with no specific treatment. Everything settles back down after the birth. Dental follow-up during pregnancy is recommended and safe.
6. A wisdom tooth coming through
The swelling is on one side only, right at the back, sometimes with difficulty opening the mouth. The gum forms a hood over the tooth pushing through, and debris builds up underneath.
What helps: cleaning the area carefully and rinsing with warm salt water. If the pain increases or you have a fever, see a professional quickly.
7. A reaction or a deficiency
Rarer: a reaction to a new toothpaste (some foaming agents irritate sensitive membranes), to a dental appliance, or a marked vitamin C deficiency that weakens the collagen in the gums.
What helps: switching to a gentle formula and observing over two weeks. Our Gentle Coconut Whitening toothpaste, known for its mildness, is a good test. On the food side, citrus fruits, kiwis and peppers easily cover your vitamin C needs.
What to do right now
- Rinse with warm salt water (half a teaspoon of salt in a glass) two to three times a day. It's simple, free, and it brings the swelling down.
- Keep brushing the area, gently. Avoiding it keeps the problem going.
- Floss every evening, even if it bleeds for the first few days.
- Don't place aspirin on the gum — an old remedy that causes chemical burns.
A Sea Salt & Baking Soda Purifying toothpaste can support this phase: sea salt has a recognised cleansing action, and baking soda helps neutralise acidity in the mouth.
FAQ
How long does a swollen gum take to go down?
If plaque is the cause and you correct your routine, allow 7 to 14 days. Once a foreign body is removed, things calm down within 48 hours. Swelling linked to tartar won't go away without a scaling.
Should you apply cold?
On a cheek that's swollen on the outside, yes, a cold cloth brings relief. Directly on the gum, go for warm salt-water rinses instead — more effective and less aggressive for the membrane.
Can a swollen gum make your teeth hurt?
Yes. The inflammation puts pressure on the ligament surrounding the root, which gives a feeling of a "sensitive" tooth or one that "moves" when you chew. It disappears along with the inflammation.
When is it urgent?
See someone without delay if you have a fever, a swollen cheek, pus, difficulty swallowing or opening your mouth. These signs suggest an abscess that needs prompt care.
Key takeaways
Diffuse, widespread swelling points to plaque or tartar; localised, sudden swelling points to a foreign body or a wisdom tooth. In every case, you never stop cleaning the area — you clean it better, and more gently. Toothpaste supports the process, but it doesn't replace a dentist's opinion if the situation lasts beyond two to three weeks.
To find the care that suits your profile, take the two-minute quiz. And if bleeding is your main symptom, our article on the first signs of gingivitis sets out what to do.