Contact allergy to oxidized geraniol among Swedish dermatitis patients-A multicentre study by the Swedish Contact Dermatitis Research Group

Antioxidant activity analysis of new interspecific hybrid germplasm thyme and oregano essential oils with different chemotypes

Thyme and oregano essential oils (EOs) and their components have numerous applications in the pharmaceutical, food, and cosmetic industries owing to their antioxidant, antibacterial, antifungal, anti-inflammatory, antiviral, and immunological properties. We attempted to create new chemotypes through the hybridization of thyme and oregano for functional EO research and product development. Here, we used interspecific hybridization to create new thyme and oregano germplasms with new EO chemotypes. The antioxidant activities of these new chemotype EOs were verified by DPPH, ABTS, and FRAP analyses. We determined that there are five types of thyme hybrid EOs: geraniol-type, carvacrol-type, thymol-type, parent polymerization-type, and α-terpineol/α-terpinyl acetate-type. Moreover, there are five types of oregano hybrid EOs: carvacrol-type, thymol-type, sabinene hydrate-type, parent polymerization-type, and carvacrol/sabinene hydrate-type. The geraniol, thymol, and carvacrol contents ranged from 30.45%, 1.21% and 0.00%, respectively, in the parents to 81.66%, 52.65%, and 46.16%, respectively, in the thyme hybrids. The carvacrol and thymol contents ranged from 2.33% to 24.18%, respectively, in the parents to 94.16% and 76.77%, respectively, in the oregano hybrids, indicating obvious heterosis. We further used three antioxidant assays, DPPH, ABTS, and FRAP, to analyse the antioxidant activity of thyme and oregano hybrid EO samples. The antioxidant capacities of carvacrol- and thymol-type EOs were significantly superior to those of other chemotypes. Our data suggest that carvacrol- and thymol-type EOs with greater antioxidant potential can be applied in many industries. In addition, the function of high geraniol-type thyme EO should be further researched. The results will also be very useful for the selection of new varieties, functional research on carvacrol-, thymol-, and geraniol-type essential oils, and product development of feed additives, cosmetics, etc.

Antioxidant and Antibacterial Activities of Chinese Native Thyme Essential Oils with Different Chemotypes

Thyme essential oils (EOs) have antioxidant, antiviral, antifungal, antibacterial, anti-inflammatory, and immunological properties and are used in medicine, food, feed additives, and cosmetics. Here, we made use of a multidimensional analytical method to analyze the differences in the chemical components, chemotypes, and antioxidant and antibacterial activities of EOs from 24 Chinese native thymes. These Chinese native thymes comprised 10 species (Thymus quinquecostatus, T. mongolicus, T. inaequalis, T. mandschuricus, T. curtus, T. amurensis, T. roseus, T. proximu, T. marschallianus, and T. altaicus) and two varieties (T. quinquecostatus var. asiaticus and T. quinquecostatus var. przewalskii). Four primary chemotype groups were identified, namely carvacrol, thymol, geraniol, and α-terpineol. The maximum carvacrol, thymol, geraniol, and α-terpineol contents were 72.4, 58.6, 59.5, and 65.4%, respectively. The antioxidant capacities of the thymol and carvacrol chemotype EOs were found to be significantly superior to the other chemotypes using three antioxidant assays: DPPH, ABTS, and FRAP. Moreover, the thymol and carvacrol EO chemotypes could significantly inhibit the growths of the common food-borne pathogenic bacteria Staphylococcus aureus and Escherichia coli. A correlation analysis between the EO components and the bacteria showed that thymol significantly positively correlated with the bacteria. In summary, we analyzed the thyme EOs' antioxidant and antibacterial activities, which laid a foundation for their use in medicines, foods, feed additives, and cosmetics. The results will also be very useful for the selection of wild thymes for functional research on carvacrol-, thymol-, geraniol-, and α-terpineol-rich essential oil chemotypes and the product development of feed additives, cosmetics, etc.

Contact allergy to oxidised geraniol may be over-represented in individuals with photocontact allergy to ketoprofen

BACKGROUND

Simultaneous overrepresentations of contact allergies and photocontact allergies are common in individuals with photocontact allergy to ketoprofen.

AIMS

To investigate whether contact allergy to oxidised (ox.) geraniol, geraniol, geranial, neral and citral is overrepresented in individuals with photocontact allergy to ketoprofen.

METHODS

The contact allergy rates to ox. geraniol, geraniol, geranial, neral and citral in routinely patch tested dermatitis patients were compared with the corresponding rates in individuals with photocontact allergy to ketoprofen.

RESULTS

Allergic patch test reactions were noted to ox. geraniol 11% (n = 39, 5.8%), ox. geraniol 6% (n = 12, 1.8%), geraniol 6% (n = 2, 0.3%), geranial (n = 18, 2.7%), neral (n = 7, 1.0%) and citral (n = 15, 2.2%). In those four patients who were diagnosed with photocontact allergy to ketoprofen during the test period, a significant overrepresentation (p = 0.020) of simultaneous contact allergy to ox. geraniol 11% was demonstrated. Overrepresentation of simultaneous contact allergy to various combinations of ox. geraniol, ox. limonene and ox. linalool was also noted in ketoprofen-photoallergic patients.

CONCLUSIONS

Contact allergy to ox. geraniol, geranial and citral is common in routinely tested dermatitis patients. There is an overrepresentation of simultaneous contact allergy to ox. geraniol, ox. limonene and ox. linalool in patients with photocontact allergy to ketoprofen.

Contact sensitization to essential oils: IVDK-data of the years 2010 - 2019

BACKGROUND

Essential oils (EOs) are widely used in cosmetics, perfumes, massage fluids, aroma therapy, and natural medicine. Some essential oils contain contact sensitizers.

OBJECTIVES

To describe the frequency of sensitization to EOs in dermatitis patients presenting in skin clinics including concomitant reactions, to evaluate the EO patch test preparations, and to identify patient groups with an increased risk of EO sensitization.

PATIENTS AND METHODS

Retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK), 2010-2019.

RESULTS

Twelve EOs were patch tested in an aimed manner in 10 930 patients, of whom 908 (8.3%) reacted to at least one EO. Only 6 EOs elicited more than 1% positive patch test reactions: ylang ylang (I + II) oil (3.9%), lemongrass oil (2.6%), jasmine absolute (1.8%), sandalwood oil (1.8%), clove oil (1.6%), and neroli oil (1.1%). Concomitant reactions among EOs or to EOs and fragrances were frequent. Among EO-positive patients, women, leg dermatitis patients, patients aged 40 years or more, masseurs and cosmeticians were over-represented.

CONCLUSIONS

Sensitization to EOs occurs, albeit infrequently in most cases. Masseurs and cosmeticians have an increased risk of sensitization to EOs. This article is protected by copyright. All rights reserved.

What is the added value of patch testing with 30 fragrance allergens in addition to the European baseline series?

Background

Patch testing with the fragrance allergy markers in the European baseline series (EBS) does not identify all patients with fragrance allergy. Hydroperoxides of linalool and limonene have been shown to be useful allergens in detecting fragrance sensitization.

Objectives

To evaluate the added value of testing with 30 fragrance allergens in addition to the EBS.

Methods

All patients with suspected fragrance allergy who underwent patch testing at the Amsterdam University Medical Centers between November 2019 and January 2021 to the EBS and fragrance series were included.

Results

Of 323 patients tested, 162 (50.2%) were found to be fragrance sensitized. The most sensitizing single allergens were the hydroperoxides of linalool (1.0 and 0.5% pet.) and limonene (0.3 and 0.2% pet.). Testing with the hydroperoxides of linalool and limonene identified 62 fragrance‐sensitized patients (38.3%) who could not be detected by the common fragrance markers. Of all fragrance‐sensitized patients, 21 (13.0%) would have been missed when not testing with the fragrance series.

Conclusions

Patch testing with the fragrance series in addition to the EBS is valuable. To reduce the risk of false‐negative reactions, it is advisable to test the hydroperoxides of linalool and limonene.

Highlights

Of the 323 patients with suspected fragrance allergy, 162 (50.2%) were found to be fragrance sensitized.

Testing with the hydroperoxides of linalool and limonene identified 62 fragrance‐sensitized patients (38.3%) who could not be detected by the European baseline series (EBS) fragrance markers. When not tested with the fragrance series, 21 (13.0%) of the sensitized patients would have been missed.

Routinely performing patch testing with the fragrance series in addition to linalool and limonene hydroperoxide as part of the EBS is recommended.

A negative breakdown test in a fragrance mix I-positive patient does not rule out contact allergy to its fragrance constituents

BACKGROUND

In about half of the patients reacting positive to fragrance mix I (FM I), breakdown testing remains negative. This raises the question of whether the reaction to FM I is false-positive, or the breakdown test is false-negative.

OBJECTIVES

To identify characteristics and sensitization patterns of patients positive to FM I, but not to its fragrance constituents.

PATIENTS AND METHODS

Retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK) between 2005 and 2019. Three patient groups were defined according to their reaction pattern: Group I, FM I positive and ≥1 single fragrance positive in the breakdown test (n = 1912); Group II, FM I positive and breakdown test negative (n = 1318); Group III, FM I negative (n = 19 790).

RESULTS

Regarding the pattern of concomitant reactions to other fragrances, Group II had an intermediate position between Group I and Group III. In other respects (age and sex distribution, frequency of sensitization to non-fragrance baseline series allergens), Group II rather resembled Group I.

CONCLUSIONS

Not every positive reaction to FM I in patients with negative breakdown tests is false-positive. There may be false-negative reactions to the single fragrance components when patch tested at 1% pet. Raising patch concentrations of some single fragrances is recommended.

Patch testing with purified and oxidized citronellol

BACKGROUND

Citronellol is a commonly used fragrance terpene included in fragrance mix II. As with many other fragrance terpenes, citronellol is susceptible to autoxidation. Citronellol hydroperoxides are formed in large amounts and are the only oxidation products identified as sensitizers in oxidized citronellol.

AIM

To compare frequencies of contact allergy to purified and oxidized citronellol and to investigate the pattern of concomitant reactions to fragrance markers of the baseline series, oxidized linalool, and oxidized limonene.

METHODS

A total of 658 dermatitis patients were patch tested with purified and oxidized citronellol at 2.0%, 4.0%, 6.0%, and 1.0%, 2.0%, 4.0%, 6.0% petrolatum, respectively. The irritant properties of purified and oxidized citronellol were studied before patch testing.

RESULTS

Few irritant reactions were observed in the pretest. Purified citronellol detected positive reactions in 0.15%-0.31% of patients, while oxidized citronellol detected positive reactions in 0.61%-4.5%. Among patients reacting to oxidized citronellol, 34%-50% showed concomitant reactions to fragrance markers of the baseline series and 75%-91% to oxidized linalool or oxidized limonene.

CONCLUSION

Oxidized citronellol detects more cases of contact allergy than purified citronellol, and these cases are not all detected using fragrance mix II. Patch testing with oxidized citronellol will add to the tools in the diagnosis of fragrance allergy.

Contact Allergy-Emerging Allergens and Public Health Impact

Contact allergy (sensitisation) and allergic contact dermatitis (ACD) resulting from it have a considerable public health impact. For the present review, all pertinent articles were systematically searched via Medline and Web of Science™; additionally, all available issues of the journals "Contact Dermatitis" and "Dermatitis" were manually searched, covering the years 2018-2019, thereby extending and re-focusing a previous similar review. New allergens, or previously described allergens found in a new exposure context or of other current importance, are described in sections according to substance classes, e.g., metals, preservatives, fragrances. As a common finding in many investigations, a lack of information on product composition has been noted, for instance, regarding a newly described allergen in canvas shoes (dimethylthiocarbamylbenzothiazole sulfide) and, most notably, absence of co-operation from manufacturers of glucose-monitoring devices and insulin pumps, respectively. These latter devices have been shown to cause severe ACD in a considerable number of diabetic patients caused by the liberation of isobornyl acrylate and N,N'-dimethylacrylamide, respectively, as demonstrated by an international collaboration between dermatologists and chemists. Improved and complete ingredient labelling for all types of products, and not just cosmetics, must be put on the legislative agenda.

Essential oils, asthma, thunderstorms, and plant gases: a prospective study of respiratory response to ambient biogenic volatile organic compounds (BVOCs)

Purpose: Prevailing opinion is that wind-pollinated plants affect asthma negatively and that insect- pollinated ones do not. "Thunderstorm" asthma, too, is attributed to bursting grass pollens. Additional biogenic volatile organic compounds (BVOCs) are identified here. Essential oils' BVOCs are inhaled from plants, oil diffusers, candles, room "fresheners", perfumes, and hygiene products. Claims of BVOC "safety" for sensitive respiratory systems are questioned. Methods: Fourteen volunteers, of mixed-age and gender, with seasonal asthma recorded peak expiratory flow (PEF) and 11 symptom scores. BVOCs were collected on Tenax tubes from ambient air in autumn and spring, as were live flower emissions, before and after a thunderstorm. Gas chromatography-mass spectrometry analysis identified frequently occurring BVOCs. Air spora, meteorological, outdoor air pollution variables, and BVOCs predict respiratory symptoms in univariate linear regression models, seasonally. Results: Increased pinene, camphor, linalool, linalyl acetate, benzaldehyde, and benzoic acid predict respiratory symptoms, including reduced PEF, and increased nasal congestion; day length, atmospheric pressure and temperature predict symptoms in both seasons, differently; other variables predict a range of symptoms (0.0001≤p≤0.05). Thunder predicts different BVOC emissions in spring, compared to autumn (p≤0.05). An uncut Grevillea flower emitted linalool and hexenal before a storm; the latter is also emitted from cut grass. Increased nitrogen oxides and pinene in autumn may combine to form harmful oxidation products. Conclusion: This research supports BVOCs as contributors to seasonal asthma and allergic rhinitis, and "thunderstorm" asthma. Pinene emissions from Myrtaceae species (Eucalyptus, Melaleuca, Leptospermum, Callistemon), Brassicaceae (canola), and conifers, worldwide, may induce respiratory inflammation and maintain it, by inhibiting eosinophilic apoptosis. Widely used essential oil products containing BVOCs, like linalool, are associated here with respiratory symptoms. Lagged responses suggest that users' cognitive associations between exposure and response are unlikely, increasing potential for impaired health for vulnerable children.