As with the use of many flavouring or fragrance-containing consumer products, ‘vaping’ e-liquid has the potential for causing an allergic reaction. An allergic reaction is an overreaction by the body’s immune system to compounds that a person is ‘allergic’ to. Even if a compound has the potential to cause such a reaction (i.e. it is an allergen), that doesn’t mean it will. Whether an allergic reaction is likely, will depend on the person’s immune system and the amount of the compound used in a product. However, some substances are more likely to be an allergen than others.
Flavourings are an important part of the vaping experience and some flavourings are known allergens. Currently, there are no specific allergy-related regulatory restrictions under either the Tobacco Products Directive in Europe or regulations administered by the Food and Drug Administration in the US.
Researchers from British American Tobacco have therefore devised a practical approach to assessing and managing the allergy risk associated with e-liquid flavourings and other ingredients (Regulatory Pharmacology and Toxicology http://dx.doi.org/10.1016/j.yrtph.2017.04.003. This guide is a follow up to their blueprint for the safe use of flavourings in e-cigs, which was published in Regulatory Pharmacology and Toxicology in 2015. (http://dx.doi:10.1016/j.yrtph.2015.05.018).
The most common allergy is contact sensitization arising when, for example, nickel jewellery touches the skin. Much less common is respiratory allergy, or ‘chemical asthma’. ‘Although respiratory allergy is much less common than skin allergy, the potential adverse effects are much more severe,’ explains Dr Sandra Costigan, Principal Toxicologist at British American Tobacco. Chronic inhalation of respiratory allergens can lead to symptoms ranging from mild breathing difficulties to fatal anaphylaxis.
For skin allergens, the researchers propose a method for estimating the exposures to e-liquid ingredients and quantitatively assessing the risk. This has then allowed them to work out a concentration of an allergen that is not expected to cause allergy in the person vaping the e-liquid.
For skin allergens, putting this into practice is relatively straightforward, as an approach to prevent contact sensitization is well established: The stronger the allergen, the lower the supportable concentration in e-liquid. Additionally, the researchers say any known allergen should be labelled as an ingredient if it is present at 0.1% concentration or higher, even if it is established that it can be used safely at a higher concentration. This will help those consumers who already know themselves to be sensitive to certain ingredients to make product choices.
For respiratory allergens, the authors use a cocoa extract as a case study, because it is used quite commonly in e-liquids. The case study showed the tolerable levels identified for the cocoa extract are not sufficiently high to allow it to perform as an effective flavouring in e-liquid. It is discussed why this is likely to be an issue for other respiratory allergens as well. They therefore recommend to just not use respiratory allergens at all.
It is quite difficult to decide whether something is or isn’t a respiratory allergen. Again, the researchers used the cocoa extract as a case study of reviewing all the evidence related to respiratory allergy for cocoa. Based on this, the researchers concluded the chance of it being a respiratory allergen is high enough to take the precaution of treating it as a respiratory allergen. They then worked out the concentration at which it could be used safely, but found the level is too low for the ingredient to provide any flavour. ‘We’d recommend against using cocoa extract in an e-liquid. The risks just aren’t worth the benefits,’ says Costigan.
Furthermore, quoting the low occupational exposure guidelines related to respiratory allergens (aimed at protecting workers against respiratory allergy from unintended exposure to allergens in the workplace), the researchers say it is prudent to exclude all known respiratory sensitisers from e-liquids. As an additional safeguard, if natural extracts are used as flavourings for which no particular data exists to decide if it is a respiratory sensitiser or not, only protein-free versions should be used. This is because most respiratory allergens from natural extracts come from the protein parts.
Food allergens are yet another type of allergen and the authors recommend the presence of any potential food allergens (that are not already excluded for being respiratory allergens as well) should be labelled.
‘No two people have the same immune response, which is why it is important to tell people about allergens in a product even if all your data says most people shouldn’t experience a problem,’ says Dr Sandra Costigan, Principal Toxicologist for vaping products at British American Tobacco.
Guide for allergy-safe use of e-liquid ingredients, including flavourings.