Fragrance sensitisers: Is inhalation an allergy risk?

It is well established that some fragrance substances have the potential to cause skin sensitisation associated with the development of allergic contact dermatitis (ACD). Fragrances are invariably relatively volatile leading to the consideration that inhalation of fragrances might be a relevant route for either the induction of allergic sensitisation or the elicitation of allergic reactions. Moreover, there has been increasing recognition that allergic sensitisation of the respiratory tract can be induced by topical exposure to certain chemical allergens. Here the central question addressed is whether inhalation exposure to fragrance allergens has the potential to cause skin and/or respiratory sensitisation via the respiratory tract, or elicit allergic symptoms in those already sensitised. In addressing those questions, the underlying immunobiology of skin and respiratory sensitisation to chemicals has been reviewed briefly, and the relevant experimental and clinical evidence considered. The essential mechanistic differences between skin and respiratory allergy appear consistent with other sources of information, including the phenomenon of ACD that can arise from topical exposure to airborne allergens, but in the absence of accompanying respiratory effects. The conclusion is that, in contrast to topical exposure (including topical exposure to airborne material), inhalation of fragrance sensitisers does not represent a health risk with respect to allergy.