An allergen is a substance that causes an allergic reaction. The most common problems observed with fragrance ingredients, either through use of a perfume or a fragranced consumer product, are skin allergies and skin irritations. To cause a skin allergy, a certain minimum amount of the fragrance substance must penetrate the skin and attach to a skin protein. Only once the fragrance substance is attached to a skin protein can it provoke a cascade of events in our immune system which ultimately ends in allergy symptoms.
Allergic reactions typically occur with a delay of about one day after using the perfume or cosmetic product, while irritant reactions develop immediately after use. However, bear in mind that skin reactions cannot necessarily be attributed alone to the fragrance ingredients contained in the product. This effect also depends on the irritation/allergenic potential of the other ingredients and their levels in the cosmetic product.
The European Commission’s Scientific Committee on Consumer Safety has identified a total of 54 individual fragrance substances and 28 natural extracts (essential oils) as ‘established contact allergens in humans’. Currently there are 26 perfume allergens that in the EU must be declared on labels of ingredients, if above 0.001% (leave-on products) or 0.01% (rinse-off products). These are:
Methyl heptine carbonate
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Finally, it is important to note the difference between a fragrance free product (i.e. a product that contains no components classified as fragrances, but which may have a proprietary scent due to certain raw materials), an unscented product (i.e. a product which has no discernible scent, but may contain components classified as fragrances) and a product with no added fragrance (which in essence means a product contains a component classified as a fragrance, but which has another primary function, such as preservation). If you are allergic to a certain fragrance component, the ingredient listing of a product will be your best guide. If you are sensitive to scents, you may react to the proprietary scent of a particular raw material, but this is not something which can necessarily inferred from an INCI list. From July 2019 and onwards the EU will no longer allow any free from-claims, and this will be applied to fragrances as well.