Safety data sheets for candles and diffusers

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This article looks at requirements for hazard classification, labelling and safety data sheet provision for makers of candles and diffusers in the EU and UK.

Essential oils are difficult substances from the regulatory standpoint because of their complex composition.

Candles and diffusers are common household products, but their regulation as potentially hazardous products is complicated by the complex chemicals used as fragrances. All products should be assessed for hazard classification.

While safety data sheets are not required for consumer use, suppliers often need to have one available.

Using default concentration thresholds sometimes lead to over-classification. Use of expert judgement and actual hazard data for ingredients can reduce the need for pictograms and statutory warning phrases.

For further information click our SDS services page, SDS content guide, or contact us.

For help with the jargon, check our glossary.

Ingredients for candles and diffusers

Candles and diffusers usually comprise an oil or wax, combined with fragrance ingredients or natural essential oils.

The oils or waxes are chemically similar to each other, but with different melting points. They are usually made up of long-chain carbon substances from either petroleum or plant origin, or from beeswax.

Essential oils are difficult substances from the regulatory standpoint because of the complex composition. They are substances of unknown and variable composition from biological origin (UVCB in legal terminology).

Essential oils can be seen as substances in their own right, or alternatively, the hazards are assigned to major components within the essential oil.

For example, lemongrass oil (INCI name: cymbopogon citratus leaf oil) has been assigned an EC number (289-752-0), indicating it is regarded as a substance. But it comprises around 75% citral (EC 226-394-6) and 5% limonene (EC 227-813-5) which are also substances.

Use pattern for candles and diffusers

Safety data sheets (SDSs) are not mandatory for hazardous products that are supplied only to the general public, provided that users are given safety information in another format.

Candles and diffusers with a hazard classification that are used in spas and salons would require a safety data sheet to be supplied at or before the point of sale, because this is professional use in a workplace.

Workers in retail outlets exposed to the products may also be regarded as a professional use.

For these reasons, many suppliers have SDSs available, even if they are not legally required.

Hazard classification for candles and diffusers

Legal provisions

Hazard classification is required for all chemical products, including candle wax and diffuser oil, except where there are specific exemptions, such as for finished cosmetic products that require their own safety assessment.

The hazard classification and labelling applies to the product as supplied. It is the wax/oil and fragrance mixture, and not the hazards generated once the candle is lit. The SDS can contain advice on hazards presented during use.

Many essential oils and fragrances are hazardous. Products containing hazardous ingredients should be assessed, as described in the Classification, Labelling and Packaging Regulation (CLP Regulation; 1272/2008).

The legal provisions for safety data sheets are given in the REACH Regulation (1907/2006), Annex II.

Candles and diffusers often contain hazardous essential oils or fragrance ingredients at concentrations which can cause the products to be classified as hazardous.

The hazard classification determines which symbols and statutory text appears on the label.

Hazard assessment

There are a few ways to conduct the hazard assessment. Specific testing is the most reliable, but it is expensive, and not mandatory.

When assessing the safety and hazard classification of a product, I usually recommend working from the individual components where the information is available, so for lemongrass oil this would be the citral and limonene. This can result in a less severe overall hazard classification.

This approach is less useful when either:

  • The essential oil or fragrance contains many ingredients at low concentration, in which case the classification becomes laborious and the safety data sheet can fill up with component information.
  • The essential oil contains unknown substances so its hazard cannot be assigned to particular components.

Fragrances are mixtures (ie a combination of substances). To assess the safety of mixtures, it is usual to calculate the product classification from its composition, ie the identity of the substances (mixture components) and their percentage in the mixture.

To further complicate this issue, many fragrance providers will not issue composition details for their products. This is because it is proprietary information and fragrance suppliers do not want their products to be copied. Instead, they issue ‘IFRA certificates’ giving the maximum safe concentration of their fragrances in specific products.

Usually for candles and diffusers, no limit is specified because the skin contact is limited, particularly compared to cosmetic products.

Generic concentration limits

The most common method for assess product hazard classification is using generic concentration limits for the ingredients.

These default concentration thresholds are given in the CLP Regulation. If the ingredient with the hazard is present above this threshold concentration, then the product should also be considered for the hazard.

The generic threshold concentrations for key hazards are given in the table below. Brexit will not change the requirements for hazard classification in the UK.

HazardGeneric concentration limit (%) and notes
Flammable liquidNo concentration limit. Determine flash point.
Acute Toxicity, oral, Category 425
Skin irritation10
Eye irritation10
Skin sensitisation, Category 11
Aspiration hazard (lung-damage if swallowed)10, but also based on the viscosity
Acute aquatic toxicity25 (can be less if particularly toxic)
Chronic aquatic toxicity0.25 for very toxic substances; M-factors can reduce this further; several parameters are considered for long-term toxicity classification
Generic concentration limits for certain hazards associated with fragrance ingredients and essential oils

These generic thresholds are likely to be used by software, for example in automated safety data sheet preparation. This can lead to a more severe hazard classification than is necessary.

Expert judgement

It is possible to override the classification obtained from using generic concentration limits using expert judgement. There are some specific instances where this can be useful.


Candles do not burn fast enough to meet the CLP classification criteria as ‘flammable solids’. Diffuser oil containing flammable fragrance ingredients should be assessed as a flammable liquid, and I recommend that the flash point is measured if there is doubt about the hazard classification.

Acute toxicity

For acute toxicity, the calculation method using the hazard classification of ingredients and generic concentration limits can give a more severe classification than necessary.

This is because the acute toxicity estimate of the ingredient derived from the ingredient classification is precautionary.

An assessor can use actual toxicity data that is publicly available to give a more accurate hazard classification, that is usually less severe than that estimated by classification software.

Irritation and sensitisation

Candles are less likely to cause sensitisation and irritation, because hazardous ingredients are bound within the solid wax matrix. The International Fragrance Association (IFRA) has stated: ‘due to the expected negligible skin exposure from such products [which includes candles and reed diffusers] the risk of induction of dermal sensitization through the normal formulation and use of such products is considered to be negligible. As such, the concentration of fragrance ingredient is not restricted in the finished product. [1]

This may allow an expert two routes of reducing the hazard classification for candles:

  • Stating that the ‘form or physical state’ in which the mixture (candle or diffuser oil) is presented means that these hazards are not present (CLP Art 6.1), so the hazard classification is not required.
  • Stating the hazardous substance is ‘not biologically available’ (CLP Art 12), so the hazard classification is not required.

Use of these derogations is controversial, and supporting evidence is recommended.

Aspiration toxicity

Essential oils sometimes have an aspiration toxicity hazard, common for low-viscosity hydrocarbon substances. The hazard relates to the possibility of lung damage after swallowing the product.

Candles, as a solid, are not an aspiration hazard.

Diffuser oil aspiration hazard is likely the same as the base oil, but it may be necessary to measure the viscosity of the mixture if there is doubt about the classification.

Aquatic toxicity

Similar to acute toxicity above, the calculation method using the hazard classification of ingredient and generic concentration limits can give a more severe classification for aquatic toxicity.

Many essential oils have a hazard classification for aquatic toxicity – indicated by the ‘dead fish, dead tree’ symbol.

An assessor can use aquatic toxicity data that is publicly available to give a more accurate hazard classification, that is usually less severe than that estimated by classification software.

Small package labelling derogations

For mixtures sold at less than 125 mL, there are legal provision to omit some of the labelling information (pictograms and hazard precautionary statements) for certain hazard types. These provision apply to flammable liquids, skin and eye irritation, and aquatic toxicity, and some other hazards (see CLP Regulation, Annex I).


[back to Irritation and sensitisation]

[1] IFRA RIFM QRA Information Booklet Version 7.1; Revised 9 July 9 2015.

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