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Essential oils may become allergenic on contact with oxygen in the air and certain skin enzymes, according to recent research.
Formulators should be aware that certain aromatic oils are altered by environmental factors and can cause contact allergies in sensitive individuals, even if the oil itself is not an allergen in its pure form, said researcher Lina Hagvall from the University of Gothenburg, Sweden. Hagvall looked at lavender oil and geraniol oil (the major component of rose oil) as part of her pHD thesis.
Lavender oil oxidizes in air
Lavender oil reacts with the oxygen in the air, forming hydroperoxides, which are strong allergens, according to Hagvall. Although Hagvall did not investigate the behaviour of lavender oil when in contact with skin enzymes, she referenced previous studies indicating it did not form allergens under these circumstances.
In contrast, geraniol oil reacted with the skin enzymes as well as oxidizing in contact with the air, forming the same allergenic compound in both cases—geranial. Geranial is also an irritant, according to Hagvall. Although the reaction in sufferers can look the same, allergens cause an immune response whereas irritants damage the surface of the skin causing inflammation.