Recently, a study was published where the effects of lavender oil on mast cell-mediated immediate-type allergic reactions in test animals were investigated. This EO inhibits dose-dependently the mast cell-dependent ear swelling response induced by an irritant administered either topically or intradermally. The same effect can be observed on passive cutaneous anaphylaxis as well as by studying the histamine release from the peritoneal mast cells. Furthermore, lavender oil exerted a significant inhibitory effect on anti-dinitrophenyl-IgE-induced tumour necrosis factor-a-secretion from these mast cells. These results show the versatility and usefulness of the EO of lavender in skincare preparations for all skin types (Kim et al., 1999).
A series of EOs belonging to the Lamiaceae family were investigated as to their systemic allergic reactions using the prick-by-prick technique with dried commercial plants and prick tests with extracts. Skin tests with inhalants were positive to grasses as well as to ones with plants of the Lamiaceae family with the exception of basil and lavender. Plants belonging to the Lamiaceae seem to show a cross-sensitivity on the basis of clinical history and in vitro and in vivo test results (Benito et al., 1996). In contrast, contact allergy reactions to various EOs used in aromatherapy, such as lavender oil, jasmine and rosewood oil, were found. Laurel, eucalyptus and pomerance (bitter orange) produced positive skin reactions, thus showing an allergic airborne contact dermatitis. A similar dermatitis was reported on inhalation of lavender fragrance in Difflam gel (Schaller et al., 1995; Rademaker, 1994; Brandao, 1986). A facial 'pillow' dermatitis due to lavender oil allergy was also reported (Coulson et al., 1999).
A toxicity profile study by the BIBRA-working group (1994) stated that lavender oil applied to human and animal skin, produced little or no irritation, but it has caused sensitization, pho-tosensitization and pigmentation in humans. Its principal effect following administration by oral, injection or inhalation routes to rodents, was sedation. Lavender oil was rapidly absorbed through intact human skin, facts which already have been reported elsewhere (see Jäger et al, 1992; Fuchs et al., 1997). It is said that airborne sesquiterpene lactones, especially, emitted from Asteraceae plants, cause allergic reactions. This should also be the case with feverfew (Tanacetum parthenium, Asteraceae), but headspace analysis of the air around the intact plant revealed mainly (~88 per cent) volatile monoterpenes (in total 41 volatiles), among them also linalool. No sesquiterpene lactones were detected, thus only the other airborne volatiles could be responsible for the 'compositae dermatitis' (Christenson et al., 1999). Twenty-two volatile compounds have been detected in the headspace of oilseed rape (Brassica napus spp. oleifera, Brassicaceae), among them linalool. These volatiles were made responsible for respiratory mucosal and conjunctival irritations. But, since only between 50 and 87 per cent of the total volatiles, emitted in all of the entrainments carried out with flowering oilseed rape plants, belong to the monoterpene fraction also other volatiles, such as dimethyl sulfide, or sabinene, or isomyrcenol, or (£)-3-hexene-1-ol could be the cause for the above mentioned irritation (Butcher et al., 1994). Also in another case, linalool and hydroxy citronellal were made responsible for a facial psoriasis caused by contact allergy to fragrance compounds in an after shave. In the meantime, according to the knowledge of the author of this review on lavender, hydroxycitronellal possesses this allergenic potential (de Groot et al., 1983). In an exhaustive test with mice linalool-oxidation products, such as lina-lyl hydroperoxide and linalyl epoxide, could be detected as real sensitisers. The furanoid form gives rise to the formation of a carbon centred reactive radical as intermediate in the skin sensi-tisation (Bezard et al, 1997). A toxicity profile study performed by the BIBRA working group (1995) found that linalool was irritant to the skin of various species of laboratory animals. In man, this monoterpene alcohol has shown only a small ability to cause skin irritation and sensitisation.
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