Is Vegemite Good for Cold Sores? Marmite Too?

If you have ever searched for cold sore remedies online, you have probably come across the claim that Vegemite or Marmite can help. Australian parenting blogs and UK health forums are full of accounts from people who swear by dabbing a little yeast extract on a cold sore and waking up to faster healing. The question — "is Vegemite good for cold sores?" — is one of the most commonly asked food-related herpes questions online.

The short answer: there is no clinical evidence that Vegemite or Marmite can treat or heal cold sores. But the longer answer is more interesting. Both spreads contain compounds — B vitamins, lysine, and in Marmite's case vitamin B12 — that have legitimate connections to immune health and herpes management. Understanding what they do and don't contain helps explain why the anecdotes persist even without clinical proof.

This article breaks down the nutritional profiles of both spreads, evaluates the theoretical basis for their use on cold sores, examines the anecdotal claims, and puts them in the context of what actually works for managing herpes simplex virus (HSV-1).

What Are Vegemite and Marmite?

Both Vegemite and Marmite are yeast extract spreads — thick, dark, intensely salty pastes made from the by-products of beer brewing. They have loyal followings in Australia and New Zealand (Vegemite) and the UK and South Africa (Marmite), typically eaten in small amounts on toast or crackers due to their powerful flavour.

Despite their similar origins, they are not identical products. Marmite is the British original, first produced in 1902 and now owned by Unilever. It has a slightly more complex, richer flavour profile with molasses undertones. Vegemite, developed in Australia in 1922 as a local alternative during a Marmite supply shortage, has a stronger, more bitter, purely savoury profile.

Nutritionally, both are concentrated sources of B vitamins and glutamates, but they differ in one key area: Marmite contains vitamin B12, while Vegemite does not (though some newer fortified Vegemite variants now include B12). This difference turns out to be relevant when evaluating the cold sore claims — because vitamin B12 has some genuine, if limited, evidence behind it for mouth ulcer management.

Nutritional Comparison Per 5g Serving

A standard serving of either spread is approximately 5 grams (about one teaspoon). At that serving size:

• Vegemite: B1 (thiamine) ~25% RDI, B2 (riboflavin) ~25% RDI, B3 (niacin) ~25% RDI, folate ~25% RDI. No vitamin B12. Lysine: approximately 50–70mg per serving.
• Marmite: B1 ~25% RDI, B2 ~25% RDI, B3 ~25% RDI, B12 ~100% RDI (full daily requirement in one serving). Lysine: approximately 50–70mg per serving.

Both are high in sodium (~170–200mg per 5g serving) and contain glutamates that give them their umami flavour.

The Anecdotal Case: Why People Think It Works

The cold sore remedy claim for Vegemite gained widespread attention after Australian blogger Mel Watts posted about applying it directly to cold sores and mouth ulcers. She reported dramatic improvements — pain reduction within hours and visible healing within a day. The post went viral in Australian parenting communities and has been shared thousands of times.

Similar accounts exist for Marmite in the UK, particularly for mouth ulcers (aphthous stomatitis) rather than herpes cold sores specifically. Many users describe topical application reducing pain and inflammation noticeably.

What Might Be Driving the Effect

A few mechanisms could explain the anecdotal relief, even without antiviral efficacy:

• Salt content: Both spreads have an extremely high sodium concentration. Salt applied topically to a cold sore creates a hypertonic environment that can draw moisture out of lesion tissue, temporarily reducing swelling and creating an environment less hospitable to bacterial secondary infection. The salt also causes the stinging sensation that users report — which may paradoxically be interpreted as evidence that "it's working."
• Glutamates and pH: The glutamic acid content and slightly acidic pH of yeast extracts may create a brief local environment unfavourable to HSV surface activity, though this effect would be transient at best.
• Placebo effect: The active, deliberate act of treating a cold sore — regardless of the agent used — is associated with reported improvement in multiple anecdotal remedy traditions. The ritual of treatment itself has psychological value.
• B vitamins: Topically applied B vitamins are not well absorbed through skin; the nutritional benefits of Vegemite or Marmite on cold sores would come primarily from ingestion, not topical application.

None of these mechanisms constitutes antiviral activity against HSV-1. The virus itself is not killed or suppressed by yeast extract. But the anecdotes are real — people do experience relief — and the salt-driven dehydration of lesion tissue may genuinely speed the resolution of the blister phase.

The Lysine Question

The most scientifically grounded reason to be interested in Vegemite and Marmite for herpes is their lysine content. Lysine is an amino acid with well-documented antiviral properties against HSV: it competes with arginine — the amino acid HSV needs to replicate — for intestinal absorption and cellular uptake. When lysine is high relative to arginine, the virus cannot replicate efficiently. This is the basis for lysine supplementation as a herpes management strategy, supported by multiple clinical studies showing 20–40% reductions in outbreak frequency.

Yeast extract spreads do contain lysine. However, a typical 5g serving provides only approximately 50–70mg of lysine. Clinical studies on lysine and herpes use doses of 1,000–3,000mg per day. You would need to eat roughly 15–60 servings of Vegemite or Marmite daily to approach clinically relevant lysine doses — far beyond any reasonable dietary use, and with a sodium intake that would be genuinely dangerous.

In other words: the lysine in yeast extract spreads is real, but at normal serving sizes it is nutritionally insignificant for herpes management. If you want to use lysine as an antiviral strategy, a dedicated lysine supplement at 1,000–1,500mg daily is the evidence-based approach — not a teaspoon of Marmite on toast.

Marmite's B12 Advantage: Real but Niche

Where Marmite genuinely stands apart from Vegemite is its vitamin B12 content. A single 5g serving of Marmite provides approximately 100% of the adult daily requirement for B12 — making it one of the best plant-based B12 sources available, which is why it is particularly valued by vegetarians and vegans.

Vitamin B12 has some genuine association with mouth ulcer management — specifically, aphthous stomatitis (canker sores), which are not caused by herpes simplex virus. A small 2009 study published in the Journal of the American Board of Family Medicine found that 1,000mcg of B12 daily reduced the frequency of canker sore recurrences compared to placebo. These are not the same as cold sores: canker sores are inflammatory lesions of unknown cause, while cold sores are caused by HSV-1 and are a viral infection.

This distinction matters for evaluating the claims. If someone is treating a canker sore with Marmite's B12, they may see genuine benefit. If they are treating an HSV cold sore with B12, the evidence does not support a meaningful effect. The two types of mouth sores are frequently confused by the general public, which may partly explain why Marmite testimonials vary so widely.

For people who are B12 deficient — a real risk for vegans, elderly individuals, and those on metformin — Marmite can be a genuinely valuable dietary addition that supports overall immune function. A well-functioning immune system helps keep herpes in latency. But this is indirect support, not a direct antiviral effect.

What Topical Application Actually Does

Applying Vegemite or Marmite directly to a cold sore is the approach described in most online accounts. From a clinical perspective, here is what topical application can and cannot achieve:

What it can do:

• The high salt concentration draws moisture from the lesion surface, which may temporarily reduce blister size and swelling
• The acidic environment may inhibit secondary bacterial contamination of open lesions
• The stinging sensation may have a mild counter-irritant effect that temporarily dulls pain perception
• Regular application keeps the lesion dry, which can promote faster crusting and healing of the blister stage

What it cannot do:

• Kill or inactivate HSV-1 at the lesion site — neither spread has virucidal activity against herpes viruses
• Prevent the outbreak from completing its natural course
• Reduce viral shedding or lower transmission risk
• Provide B vitamin or lysine benefit through the skin — these compounds are not meaningfully absorbed transdermally

Topical application may cause stinging and irritation, especially on cracked or open lesions. For some users, this irritation is uncomfortable enough to outweigh any perceived benefit. People with sensitive skin should be particularly cautious.

If you want a natural topical option with genuine antiviral evidence, medical-grade manuka honey (UMF 15+) and topical lemon balm extract have clinical evidence behind them that Vegemite and Marmite do not. Our article on the strongest natural antivirals for herpes covers both in detail.

Dietary Use vs. Topical Use: A Different Calculation

The case for Vegemite and Marmite as dietary additions for people managing herpes is stronger than the case for topical use — even if it falls far short of therapeutic significance on its own.

Eaten regularly as part of a varied diet, both spreads contribute B vitamins that support immune function, nerve health, and overall energy metabolism. Marmite specifically provides B12 that is otherwise difficult to obtain from plant-based diets. A well-nourished immune system is more effective at keeping HSV dormant between outbreaks, so the indirect contribution of B vitamins to herpes management is not nothing — it just is not the specific antiviral action that the cold sore remedy narrative implies.

For practical dietary management of herpes, the most evidence-based approach remains:

• Maintaining a high lysine-to-arginine ratio in your daily diet (check our lysine-arginine food database for specific foods)
• Lysine supplementation at 1,000–1,500mg daily if dietary lysine is insufficient
• Adequate B12, zinc, vitamin D, and folate for overall immune competence
• Stress management and consistent sleep as the most important non-dietary factors

Vegemite and Marmite can be enjoyed as nutritious condiments that contribute to B vitamin intake in a tasty way. They are not cold sore treatments.