Propolis for Canker Sores — Mechanism and Evidence Review

TL;DR

Propolis is a sticky resin bees make from plant material. In the lab it has anti-inflammatory and antibacterial effects, and a small number of clinical trials suggest it may help canker sores. A 2024 review of 10 randomized trials with 825 people found that propolis may shorten healing and reduce pain and redness, but rated the certainty of that evidence as very low, mainly because the trials were small and varied a lot (Roberts et al., 2024 — PMID: 38248221). One small trial is worth knowing about because it tested prevention: people who took propolis capsules by mouth every day had fewer outbreaks than people on placebo (Samet et al., 2007 — PMID: 17285269). The biggest practical caution is allergy. Propolis is a well-known cause of allergic skin and mouth reactions, and anyone allergic to bee products, or who has reacted to propolis-containing cosmetics, should avoid it. It's a reasonable thing to try if you're not allergic, but it's not proven, and it's not a substitute for checking the basics like B12, iron, folate, and SLS-free toothpaste.

What Propolis Is

Bees collect resin from tree buds and sap and mix it with beeswax and their own secretions to make propolis, which they use to seal gaps and keep the hive clean. Its chemistry depends heavily on where it comes from. European propolis is mostly made from poplar trees and is rich in flavonoids and in a compound called caffeic acid phenethyl ester (CAPE). Brazilian green propolis comes from a different plant and has a different profile, including a compound called artepillin C.

That variation is one reason propolis research is hard to pin down. Two products both labeled "propolis" can contain quite different mixtures, so a result from one study doesn't necessarily apply to another product.

Why It Might Help

Anti-inflammatory effects

Canker sores are driven by inflammation, so propolis's anti-inflammatory activity is the main reason people are interested in it. The best-studied component, CAPE, blocks a central switch for inflammation called NF-κB. In lab studies using cell lines, CAPE stopped NF-κB from moving into the cell nucleus, where it turns on inflammatory genes (Natarajan et al., 1996 — PMID: 8799159). Other propolis compounds, including flavonoids like quercetin, also have anti-inflammatory effects in the lab.

The catch is that these are lab findings in cells. Whether propolis applied to a canker sore, or swallowed as a capsule, reaches the tissue in amounts that make a difference is a separate question that only clinical trials can answer.

Antibacterial effects

Propolis kills or slows many bacteria and fungi in lab tests. That's useful for keeping an open sore clean, but canker sores aren't caused by infection. They're caused by the immune system attacking the lining of the mouth. So the antibacterial effect is a side benefit at most. See What Causes Canker Sores.

Wound healing

Animal studies have found that propolis can help wounds heal. There's no good human evidence yet showing that it speeds the healing of mouth ulcers specifically, beyond the small trials described below.

What the Trials Show

The prevention trial

The most interesting study tested whether propolis could prevent outbreaks rather than treat them. In a small placebo-controlled pilot trial, people with recurring canker sores took 500 mg of propolis by mouth every day. Compared with the placebo group, they reported fewer outbreaks and a better quality of life over the study period (Samet et al., 2007 — PMID: 17285269).

It's a small pilot study, and the result was modest, so it needs confirming. But it's notable for two reasons: it's one of the few positive prevention trials for any natural product, and it used capsules taken by mouth, not a gel applied to the sore.

Treating active sores

Most of the other trials tested propolis applied in the mouth, as a gel, mouthwash, or spray, during an outbreak. A 2024 systematic review pulled together 10 randomized trials with 825 people. Overall, propolis may shorten healing time and reduce pain and redness compared with controls (Roberts et al., 2024 — PMID: 38248221).

The reviewers rated the certainty of that evidence as very low. The trials were small, used many different propolis products at different strengths, compared them with different things, and measured results in different ways. Several had a high risk of bias. So the honest summary is: the direction is encouraging, but nobody can tell you with confidence how much it helps, or which product and dose works best.

What the evidence doesn't show

• There's no large, high-quality trial of propolis for canker sores.
• There's no good evidence about which form or dose works best.
• There's no trial comparing propolis directly with the standard prescription treatment (steroid gels) in a way that would let you rank them.

Allergy: The Main Caution

Propolis is one of the better-known causes of allergic contact reactions among natural products. People who use propolis-containing lip balms, cosmetics, throat sprays, or "natural" toothpastes sometimes develop itchy, red, swollen, or peeling skin or lips, or soreness and swelling in the mouth. A mouth reaction can be confused with the canker sore you were trying to treat.

Avoid propolis if you:

• Are allergic to bees, bee stings, honey, or other bee products
• Have reacted to propolis or "bee glue" in cosmetics or lip balms before
• Have a history of allergy to balsam of Peru or fragrances, which share some components
• Have asthma triggered by allergens, unless your doctor says it's fine

If you try it: test a tiny amount first, and stop if your lips or mouth become more red, swollen, itchy, or sore than before. Don't keep using it to "push through" a reaction.

Propolis may also slow blood clotting slightly, so check with your doctor if you take blood thinners or have surgery coming up.

Forms of Propolis

• Capsules or tablets by mouth. The form used in the prevention trial. Taken daily, not just during outbreaks.
• Gels and pastes. Applied to the sore. Stay in place better than liquids.
• Mouthwashes and sprays. Easy to use, but contact time with any one sore is short.
• Tinctures. Usually alcohol-based. They deliver a lot of the active compounds but sting on an open sore, and alcohol is irritating to healing tissue in its own right. See Alcohol and Canker Sores.

Because the products and trials vary so much, there's no proven "best" form. If you want to try propolis to prevent outbreaks, capsules match the one prevention trial. If you want to try it on an active sore, a gel is gentler than a tincture.

If you're not allergic to bee products and want to try it:

How Propolis Compares to Other Options

Stronger evidence than propolis:

• Prescription steroid gels: reduce pain and help sores heal faster than placebo; the standard treatment
• Vitamin B12: a placebo-controlled trial showing fewer outbreaks over six months
• Honey: several small randomized trials in which it did as well as or better than a steroid paste (El-Haddad et al., 2014 — PMID: 25019115; Ghalwash et al., 2025 — PMID: 39723829)

Similar level of evidence:

• Aloe vera gel: a few small trials
• Probiotics: small trials with mixed results

Weaker or no evidence:

• Coconut oil, baking soda, and vitamin E: no trials for canker sores
• Hydrogen peroxide and apple cider vinegar: likely to irritate healing tissue

Should You Try It?

Propolis is a reasonable thing to try if you aren't allergic and you've already covered the basics:

1. Get tested for low B12, iron, folate, and zinc.
2. Switch to an SLS-free toothpaste.
3. Look at stress, sleep, and food triggers.

If you try it for prevention, take it daily for at least three months and keep a record of when sores appear, so you can actually tell whether it's doing anything. If you try it on an active sore, start with a small test amount.

While you're waiting for a sore to heal, a barrier patch protects it from food and your teeth without any risk of an allergic reaction: