Do essential oils kill mould? What the evidence shows
Some essential oils inhibit mould growth or reduce the number of viable fungi in laboratory tests. How well they work depends on the oil, the fungus, the concentration and the way they are used.
For mould at home, moisture control and cleaning come first. Here is how to read the oil research without expecting more from a bottle than the test measured.
What does “kills mould” mean?
Three kinds of evidence often get mixed together:
- Contact tests: a measured amount of oil or formulation touches the fungus. Surface type, concentration and contact time affect the result.
- Vapour experiments: fungi are exposed to volatile compounds in a defined setup. Air volume, delivery method and exposure matter.
- Household outcomes: whether a product helps with mould in an actual building, with changing humidity, ventilation and materials.
Also check whether a study measured reduced growth or fewer surviving fungi. Growth inhibition alone does not prove that the mould was killed.
Which oils have evidence against mould?
A 2015 study by Rogawansamy and colleagues found that tea tree oil inhibited Aspergillus fumigatus and Penicillium chrysogenum in laboratory liquid and vapour tests. This measured fungal growth under controlled conditions.
A 2024 paper by Wang and colleagues examined how eugenol and citral together affected the cell membrane of Aspergillus niger. It helps explain antifungal activity at a molecular level.
These studies give us evidence about particular oils or compounds. When comparing products, look for a test of the finished formulation you will actually buy.
What about mould spores in the air?
A 2022 UNSW study found fewer viable Aspergillus flavus spores after researchers passed aerosols through vapour from SAN-AIR Mould Gone gel in a small glass chamber. SAN-AIR supplied funding and material for the study.
That result belongs to the gel and setup tested. First Light and household diffusers were outside the study.
What does First Light's 99.2% result show?
Our testing summary reports a 99.2% reduction in Aspergillus niger using the BS EN 13697:2023 surface method: undiluted First Light, direct contact and 15 minutes under controlled laboratory conditions.
Its scope is that contact test. It does not establish whole-room vapour efficacy, lasting prevention, health protection or effectiveness against every mould. Using the test method should not be described as passing the standard.
The bread comparison on our Proof page is a separate observation rather than a controlled household trial. If you are considering First Light for diffusion, read its directions alongside the testing summary.
What should you do about mould at home?
NSW Health's mould guidance starts with reducing dampness. Find the source before spending money on another treatment.
For a step-by-step moisture check, use our mould prevention guide.
- Check moisture and ventilation. Look for leaks and condensation. Use exhaust fans for moisture-producing activities and arrange repairs where needed.
- Clean and dry the affected area. For suitable hard surfaces, the US EPA recommends detergent and water, followed by complete drying. Follow surface and product instructions. Mouldy porous materials may need professional cleaning or replacement.
- Get help where needed. Extensive growth, substantial water damage, suspected ventilation-system contamination or an unclear source warrants professional assessment.
If a musty smell persists, look for its source. For cupboards and fabrics, see our guide to mould in a wardrobe and on clothes.
Should you make an essential-oil mould spray?
The studies above give no tested home recipe to follow. A few drops in water will not reproduce their formulations or concentrations.
Use each product for its stated purpose. A diffusion blend may be unsuitable for spraying on paint, grout or fabric. Check the current label and, for First Light, our product-use information.
Before buying a product for mould, ask what was tested, how it was applied and whether that matches the claim on the bottle.
Essential oils and mould: quick answers
Do essential oils kill mould, or just slow its growth?
It depends on the test. Growth inhibition means less growth under the study conditions. A reduction in viable fungi measures how many survived. Check which outcome the product claim refers to.
Will an essential oil diffuser get rid of household mould?
The studies discussed here do not establish that outcome. Household mould still needs moisture control, cleaning and attention to damaged materials.
What is the best essential oil for mould?
These studies do not establish one best oil for every mould problem. Look for evidence covering the finished formulation, the fungus tested and the intended use.
Does First Light’s 99.2% result apply to diffusion?
No. It applies to undiluted First Light in direct contact with Aspergillus niger for 15 minutes under laboratory conditions.
By Ben, founder of Aurala Naturals. Updated October 2026.
