Air-oxidized linalool-a frequent cause of fragrance contact allergy

Pediatric Patch Testing at Mayo Clinic Between 2016 and 2020

Background: Allergic contact Dermatitis (ACD) is a common condition within the pediatric population. Patch testing is an important way to identify relevant allergens. Objective: To provide an update of the common contact allergens seen in children based on patch testing data at our institution from 2016 to 2020. Methods: We performed a retrospective analysis of patch test data from children aged 1-18 years from 2016 to 2020 at Mayo Clinic. Reaction rates were compared to the rates reported by the Pediatric Contact Dermatitis Registry (PCDR). Results: One hundred ninety-two children aged 1-18 were patch tested to various allergens. A total of 15,457 allergens were tested, with 291 positive tests. The top 5 allergens with highest positive reaction rates were hydroperoxides of linalool, hydroperoxides of limonene, methylisothiazolinone, nickel, and cobalt. Seven of the top 38 allergens with the highest reaction rates are not currently included in the Mayo Clinic Pediatric Patch Test Series, and 11 are not currently included in the Pediatric Baseline Series (as developed by the Pediatric Contact Dermatitis Workgroup). Conclusions: Patch testing is a useful tool to diagnose children with ACD. With new products and exposures, there is an opportunity to expand current pediatric patch testing series.

Patch testing hydroperoxides of limonene and linalool in consecutive patients-Results of the IVDK 2018-2020

BACKGROUND

Hydroperoxides of limonene (Lim-OOHs) and linalool (Lin-OOHs) are potent contact sensitizers.

OBJECTIVES

To investigate the prevalence of positive patch test (PT) reactions to Lim-OOHs and Lin-OOHs in consecutive patients, their demographic factors and concomitant reactions.

METHODS

Between 7/2018 and 12/2020, Lim-OOHs 0.3% pet. and Lin-OOHs 1% pet. were patch tested in 5511 consecutive patients. We assessed PT reactivity and analysed data from patients with either positive or negative PTs to Lim-OOHs and Lin-OOHs.

RESULTS

Positive PT results to Lim-OOHs (n = 170, 3.1%) and Lin-OOHs (n = 483, 8.8%) were frequent. Most of the positive reactions were weak (LimOOHs n = 134/LinOOHs n = 429), and even more frequently, doubtful (n = 252/n = 578) or irritant reactions (n = 81/n = 178) were documented. PT reactivity to Lim-OOHs and Lin-OOHs was increased in patients with irritant reactions to sodium lauryl sulphate (SLS). The proportion of leg dermatitis and concomitant positive reactions to fragrances and essential oils was increased in patients with reactivity to these hydroperoxides.

CONCLUSION

The observed reaction pattern suggests that both test preparations display an irritant potential with an increased risk of false positive reactions. Preparations should be chemically monitored in order to reduce irritancy. Mindful interpretation of PT results and aimed patch testing of lower concentrations is recommended.

North American Contact Dermatitis Group Patch Test Results: 2019-2020

Background: Patch testing is an important diagnostic tool for assessment of allergic contact dermatitis (ACD). Objective: This study documents the North American Contact Dermatitis Group (NACDG) patch testing results from January 1, 2019, to December 31, 2020. Methods: At 13 centers in North America, patients were tested in a standardized manner with a screening series of 80 allergens, and, as indicated, supplemental allergens. Results: Overall, 4121 patients were tested; 2871 (69.7%) had at least 1 positive/allergic patch test reaction and 2095 patients (51.2%) had a primary diagnosis of ACD. The most commonly positive allergens were nickel (18.2%), methylisothiazolinone (MI) (13.8%), fragrance mix (FM) I (12.8%), hydroperoxides of linalool (HPL) (11.1%), and benzisothiazolinone (BIT) (10.4%). Compared with that of 2017-2018, prevalence of top 20 allergens statistically increased for FM I, HPL, BIT, propolis, and hydroperoxides of limonene (3.5%). For the first time, MI positivity did not increase between reporting periods. Approximately one-fifth of patients (20.3%) had ≥1 clinically relevant reaction(s) to allergens/substances not on the NACDG series. Conclusions: The epidemic of MI contact allergy in North America may have reached a plateau. Patch testing using a robust screening series, and supplemental allergens as indicated, is necessary for comprehensive evaluation of ACD.

Electron paramagnetic resonance and spin trapping to detect free radicals from allergenic hydroperoxides in contact with the skin: from the molecule to the tissue

A major research topic consists of revealing the contribution of radical-mediated reactions in dermatological diseases related to xenobiotic-induced stress, to succeed risk assessment procedures protecting producers and consumers. Allergic contact dermatitis is the clinically relevant consequence of skin sensitization, one of the most critical occupational and environmental health issues related to xenobiotics exposure. The first key event identified for the skin sensitization process to a chemical is its aptitude to react with epidermal proteins and form antigenic structures that will further trigger the immune response. Many chemical sensitizers are suspected to react through mechanisms involving radical intermediates. This review focuses on recent progress we have accomplished over the last few years studying radical intermediates derived from skin sensitizing chemicals by electron paramagnetic resonance in combination with the spin trapping technique. Our work is carried out "from the molecule", performing studies in solution, "to the tissue", by the development of a methodology on a reconstructed human epidermis model, very close in terms of histology and metabolic/enzymatic activity to real human epidermis, that can be used as suitable biological tissue model. The benefits are to test chemicals under conditions close to human use and real-life sensitization exposures and benefit from the 3D microenvironment. This article is protected by copyright. All rights reserved.

Low Prevalence of Fragrance Contact Allergy Among Turkish Population: A 24-Year, Cross-Sectional, Tertiary Single-Center, Retrospective Study

BACKGROUND

Limited data exist on fragrance contact allergy among Turkish population.

OBJECTIVE

The aim of this study was to investigate the frequency and characteristics of fragrance contact allergy in Turkey.

METHODS

A retrospective cohort study was conducted on 2566 patients consecutively patch tested with the European baseline series and additionally with a fragrance series (n = 358) at a tertiary referral center between 1996 and 2019.

RESULTS

One hundred sixty-three patients (6.4%) (male/female, 1.5:1) were sensitized with at least 1 fragrance allergen. Fragrance mix (FM) I was most frequently positive (3.9%), followed by Myroxylon pereirae (3.1%), FM II (2%), and hydroxyisohexyl 3-cyclohexene carboxaldehyde (0.5%), the latter exclusively positive in FM II-positive patients. Among 358 patients patch tested with a fragrance series, positive patch test reactions were observed in 38 patients, including 8 who did not react to baseline fragrance markers. Clinically relevant fragrance allergy was established in 128 patients (78.5%) from nonoccupational (72.4%) and occupational (6.1%) sources.

CONCLUSIONS

The low prevalence, the middle-aged male preponderance, and the predominant involvement of hands were unusual findings. Rose/citrus-flavored perfumes and eau de cologne, which are traditionally preferred in our country, were important elicitors of fragrance contact allergy, especially among middle-aged and older men.

Contact allergy to oxidized linalool and oxidized limonene: Patch testing in consecutive patients with dermatitis

BACKGROUND

Contact allergy to oxidized (ox.) linalool and ox. limonene has been reported to have a high prevalence, raising the question of inclusion into the baseline series. However, several important issues should be clarified and further investigated before inclusion can be warranted.

OBJECTIVES

To report the trends of ox. terpenes allergy in patients with dermatitis, features of the patch test reactions, and clinical characteristics of the patients.

METHODS

A retrospective analysis of 5773 patients was performed. All patients were patch tested with baseline series, individual ingredients of fragrance mix I and II, ox. linalool, and ox. limonene from 2013 to 2020.

RESULTS

The prevalence rates of contact allergy to ox. linalool and ox. limonene were 7.0% and 5.1%, respectively. Significantly increasing trends of contact allergy were observed. More than 95% of contact allergy cases were identified on Day 3/4. Patients with contact allergy to ox. linalool and ox. limonene were significantly younger than those with contact allergy to other fragrances and were predominantly female. Strong reactions were associated with older age and multiple fragrance allergies.

CONCLUSIONS

Contact allergy to ox. linalool and ox. limonene is becoming increasingly important, and findings show intriguing features. More studies concerning the clinical relevance before recommending these substances for screening are required.

One hundred years of allergic contact dermatitis due to oxidized terpenes: What we can learn from old research on turpentine allergy

Although in recent years the focus on sensitizing terpene oxidation products has been on oxidized limonene and linalool, the autoxidation of terpenes in relation to allergic contact dermatitis is not new and dates back to the early part of the 20th century with the use of turpentine causing occupational contact dermatitis in painters. This review is written in a way as to allow us to get closer to the work of the scientists in earlier days, to participate in the successes, and also to observe the weak points. The researchers concluded that the main culprit in Scandinavian turpentine was Δ³ -carene hydroperoxides. This explains its high sensitizing effect compared with French turpentine which is of the Iberian type with no or only traces of Δ³ -carene. Historical exposure to turpentine showed that ending the industrial exposure stopped the occupational skin sensitization. Patch test studies demonstrated that monoterpene hydroperoxides, far from being an obsolete source of contact allergy solely related to turpentine, is a common cause of contact allergy in the population. A hundred years of extensive chemical and clinical studies worldwide should be sufficient to meet the evidence requirement regarding allergic contact dermatitis caused by terpenes. HIGHLIGHTS: The autoxidation of terpenes in relation to allergic contact dermatitis is not new and dates back to the early part of the 20th century with the use of turpentine. The main culprit in Scandinavian turpentine was Δ³ -carene hydroperoxides. This explains its high sensitizing effect compared with French turpentine with no or only traces of Δ³ -carene. Recent patch test studies demonstrated that monoterpene hydroperoxides, far from being an obsolete source of contact allergy solely related to turpentine, is a common cause of contact allergy in the population.

Structured diagnostic assessment of hand eczema in cleaning workers

Hand dermatitis is a widespread problem among cleaners. In most cases, it is caused by a combination of wet work and contact with irritants, which can result in irritant (toxic) contact dermatitis. In some cases, the irritant contact eczema then evolves into allergic contact dermatitis, although not all cases of allergic contact dermatitis are preceded by irritant contact dermatitis. This mini-review proposes a two-step diagnostic algorithm based on patch testing, which can be used if allergic contact dermatitis is suspected in cleaning workers. As a first step, we recommend performing the DKG standard series (German Contact allergy research group, DKG), the DKG rubber series, both DKG "further fragrances" series as well as the DKG preservative and disinfectant series. If there are clear hints of an occupational contact dermatitis, the first step can also involve testing patients' own products alongside the standardized tests. In a second step (at the latest), if standardized tests do not suffice to identify the culprit allergen and there is well-founded suspicion, we recommend testing the patients' own products. If necessary, the second step can also include testing the individual contact allergens contained in the screening mixes that are part of the standard series.

Aniba rosaeodora (Var. amazonica Ducke) Essential Oil: Chemical Composition, Antibacterial, Antioxidant and Antitrypanosomal Activity

Aniba rosaeodora is one of the most widely used plants in the perfumery industry, being used as medicinal plant in the Brazilian Amazon. This work aimed to evaluate the chemical composition of A. rosaeodora essential oil and its biological activities. A. rosaeodora essential oil presented linalool (93.60%) as its major compound. The A. rosaeodora essential oil and linalool showed activity against all the bacteria strains tested, standard strains and marine environment bacteria, with the lower minimum inhibitory concentration being observed for S. aureus. An efficient antioxidant activity of A. rosaeodora essential oil and linalool (EC₅₀: 15.46 and 6.78 µg/mL, respectively) was evidenced by the inhibition of the 2,2-azinobis- (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical. The antitrypanosomal activity of A. rosaeodora essential oil and linalool was observed at high concentrations against epimatigote forms (inhibitory concentration for 50% of parasites (IC₅₀): 150.5 ± 1.08 and 198.6 ± 1.12 µg/mL, respectively), and even higher against intracellular amastigotes of T. cruzi (IC₅₀: 911.6 ± 1.15 and 249.6 ± 1.18 µg/mL, respectively). Both A. rosaeodora essential oil and linalool did not exhibit a cytotoxic effect in BALB/c peritoneal macrophages, and both reduced nitrite levels in unstimulated cells revealing a potential effect in NO production. These data revealed the pharmacological potential of A. rosaeodora essential oil and linalool, encouraging further studies.

Mechanistic Insights on Skin Sensitization to Linalool Hydroperoxides: EPR Evidence on Radical Intermediates Formation in Reconstructed Human Epidermis and 13C NMR Reactivity Studies with Thiol Residues

Linalool is one of the most commonly used fragrance terpenes in consumer products. While pure linalool is considered as non-allergenic because it has a very low skin sensitization potential, its autoxidation on air leads to allylic hydroperoxides that have been shown to be major skin sensitizers. These hydroperoxides have the potential to form antigens via radical mechanisms. In order to obtain in-depth insights of such reactivity, we first investigated the formation of free radicals derived from linalool hydroperoxides in situ in a model of human reconstructed epidermis by electron paramagnetic resonance combined with spin trapping. The formation of carbon- and oxygen-centered radical species derived from the hydroperoxides was especially evidenced in an epidermis model, mimicking human skin and thus closer to what may happen in vivo. To further investigate these results, we synthesized linalool hydroperoxides containing a ¹³C-substitution at positions precursor of carbon radicals to elucidate if one of these positions could react with cysteine, its thiol chemical function being one of the most labile groups prone to react through radical mechanisms. Reactions were followed by mono- and bidimensional ¹³C NMR. We validated that carbon radicals derived from allylic hydrogen abstraction by the initially formed alkoxyl radical and/or from its β-scission can alter directly the lateral chain of cysteine forming adducts via radical processes. Such results provide an original vision on the mechanisms likely involved in the reaction with thiol groups that might be present in the skin environment. Consequently, the present findings are a step ahead toward the understanding of protein binding processes to allergenic allylic hydroperoxides of linalool through the involvement of free radical species and thus of their sensitizing potential.

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.

Inclusion Complex of Exocarpium Citri Grandis Essential Oil with β-Cyclodextrin: Characterization, Stability, and Antioxidant Activity

The purpose of this study was to produce and characterize an inclusion complex between β-cyclodextrin (β-CD) and Exocarpium Citri Grandis essential oil (EEO), and to evaluate its antioxidant properties. The volatile compounds of EEO were characterized by gas chromatography-mass spectrometer. A comparison of the β-CD, EEO, and the physical mixture with the inclusion complex revealed differences in their thermal stabilities and morphologies, which confirmed the formation of the β-CD-EEO inclusion complex. Complexed with β-CD, the β-CD-EEO inclusion complex showed a higher stability and antioxidant activity when compared with physical mixture and EEO. Therefore, β-CD can be used to form inclusion complexes with EEO to expand its potential applications in the food and drug industries. PRACTICAL APPLICATION: Exocarpium Citri Grandis is rich in essential oil and other ingredients. The optimized extraction, constituent composition, and encapsulation of EEO in β-CD were investigated in this study. The results showed that the encapsulation process increased the antioxidant activity and stability of EEO, which provides both fundamental and practical knowledge for the application of EEO in the food and drug industries.

Sensitization potential and potency of terpene hydroperoxides in the cocultured activation test method

BACKGROUND

Positive patch test reactions to mixtures of oxidized terpenes containing allergenic hydroperoxides are frequently reported. However, human sensitization data for these hydroperoxides are not available.

OBJECTIVES

To analyse and evaluate the human sensitization potential and potency of hydroperoxides in vitro by using human cells.

MATERIALS/METHODS

Limonene-1-hydroperoxide, limonene-2-hydroperoxide, citronellol-7-hydroperoxide, cumene hydroperoxide, 1-(1-hydroperoxy-1-methylethyl)cyclohexene and mixtures of citronellol hydroperoxides (isomers at positions 6 and 7) and linalool hydroperoxides (isomers at positions 6 and 7) were studied. All compounds were synthesized except for cumene hydroperoxide, which was commercially available. Their potential and potency to activate dendritic cells (DCs) was evaluated by measuring the upregulation of CD86 and CD54 on THP-1 cells upon exposure in the cocultured activation test (COCAT) consisting of HaCaT cells (human keratinocyte cell line) and THP-1 monocytes (as a surrogate for DCs).

RESULTS

Hydroperoxides upregulated CD86 and/or CD54 on cocultured THP-1 cells in a concentration-dependent manner. The results are comparable with their sensitization potency ranking in predictive animal models.

CONCLUSIONS

For the first time, the human sensitization potential and potency of several hydroperoxides were determined by the use of human cells and the COCAT method.

Contact sensitization to hydroperoxides of limonene and linalool: Results of consecutive patch testing and clinical relevance

Background

Hydroperoxides of limonene and linalool are potent sensitizers.

Objectives

To investigate the prevalence of contact allergy to both hydroperoxides of limonene and hydroperoxides of linalool, to report clinical relevance, and to investigate patient demographics.

Methods

A total of 821 patients (35.6% male, mean age 42.4 years ± 17.8 years) were consecutively patch tested with our departmental baseline series and our fragrance series, including hydroperoxides of limonene 0.3% pet. and hydroperoxides of linalool 1.0% pet. The clinical relevance was assessed for all positive reactions.

Results

Positive patch test reactions to hydroperoxides of limonene and to hydroperoxides of linalool were observed in 77 patients (9.4%, 95% confidence interval [CI]: 7.4%‐11.4%) and in 96 patients (11.7%, 95%CI: 9.5%‐13.9%), respectively; 38 of these patients (4.6%, 95%CI: 3.2%‐6.0%) reacted to both. Most reactions were considered to be possibly or probably clinically relevant (66.3% and 68.8%, respectively), and a small proportion were deemed to be of certain clinical relevance (18.2% and 19.8%, respectively).

Conclusion

As compared with previous studies, high numbers of positive reactions to both hydroperoxides of limonene and hydroperoxides of linalool were observed, the majority of which were clinically relevant, supporting their inclusion in the European baseline series.

Recommendation to test limonene hydroperoxides 0·3% and linalool hydroperoxides 1·0% in the British baseline patch test series

BACKGROUND

There is a significant rate of sensitization worldwide to the oxidized fragrance terpenes limonene and linalool. Patch testing to oxidized terpenes is not routinely carried out; the ideal patch test concentration is unknown.

OBJECTIVES

To determine the best test concentrations for limonene and linalool hydroperoxides, added to the British baseline patch test series, to optimize detection of true allergy and to minimize irritant reactions.

METHODS

During 2013-2014, 4563 consecutive patients in 12 U.K. centres were tested to hydroperoxides of limonene in petrolatum (pet.) 0·3%, 0·2% and 0·1%, and hydroperoxides of linalool 1·0%, 0·5% and 0·25% pet. Irritant reactions were recorded separately from doubtful reactions. Concomitant reactions to other fragrance markers and clinical relevance were documented.

RESULTS

Limonene hydroperoxide 0·3% gave positive reactions in 241 (5·3%) patients, irritant reactions in 93 (2·0%) and doubtful reactions in 110 (2·4%). Linalool hydroperoxide 1·0% gave positive reactions in 352 (7·7%), irritant reactions in 178 (3·9%) and doubtful reactions in 132 (2·9%). A total of 119 patients with crescendo reactions to 0·3% limonene would have been missed if only tested with 0·1% and 131 patients with crescendo reactions to 1·0% linalool would have been missed if only tested with 0·25%. In almost two-thirds of patients with positive patch tests to limonene and linalool the reaction was clinically relevant. The majority of patients did not react to any fragrance marker in the baseline series.

CONCLUSIONS

We recommend that limonene hydroperoxides be tested at 0·3% and linalool hydroperoxides at 1·0% in the British baseline patch test series.

Non-mix fragrances are top sensitizers in consecutive dermatitis patients - a cross-sectional study of the 26 EU-labelled fragrance allergens

BACKGROUND

For cosmetics, it is mandatory to label 26 fragrance substances, including all constituents of fragrance mix I (FM I) and fragrance mix II (FM II). Earlier reports have not included oxidized R-limonene [hydroperoxides of R-limonene (Lim-OOH)] and oxidized linalool [hydroperoxides of linalool (Lin-OOH)], and breakdown testing of FM I and FM II has mainly been performed in selected, mix-positive patients.

OBJECTIVES

To report the prevalence of sensitization to the 26 fragrances, and to assess concomitant reactivity to FM I and/or FM II.

METHODS

A cross-sectional study on consecutive dermatitis patients patch tested with the 26 fragrances and the European baseline series from 2010 to 2015 at a single university clinic was performed.

RESULTS

Of 6004 patients, 940 (15.7%, 95%CI: 14.7-16.6%) were fragrance-sensitized. Regarding the single fragrances, most patients were sensitized to Lin-OOH (3.9%), Evernia furfuracea (3.0%), Lim-OOH (2.5%), and hydroxyisohexyl 3-cyclohexene carboxaldehyde (2.1%). Significantly fewer patients were 'FM I-positive and constituent-positive' than 'FM II-positive and constituent-positive' (32.7% versus 57.0%, p < 0.0001). Additionally, significantly more patients were 'FM II-negative but constituent-positive' than 'FM I-negative but constituent-positive' (12.4% versus 3.2%, p = 0.0008).

CONCLUSIONS

Non-mix fragrances are the most important single fragrance allergens among consecutive patients. The test concentration of the single FM I constituents should be increased when possible.

Fragrance contact allergens in 5588 cosmetic products identified through a novel smartphone application

BACKGROUND

More than 25% of the adult European population suffers from contact allergy, with fragrance substances recognized as one of the main causes. Since 2005, 26 fragrance contact allergens have been mandatory to label in cosmetic products within the EU if present at 10 ppm or above in leave-on and 100 ppm or above in wash-off cosmetics.

OBJECTIVE

To examine exposure, based on ingredient labelling, to the 26 fragrances in a sample of 5588 fragranced cosmetic products.

METHODS

The investigated products were identified through a novel, non-profit smartphone application (app), designed to provide information to consumers about chemical substances in cosmetic products. Products registered through the app between December 2015 and October 2016 were label checked according to International Nomenclature of Cosmetic Ingredients (INCI) for the presence of the 26 fragrance substances or the wording 'fragrance/parfum/aroma'.

RESULTS

The largest product categories investigated were 'cream, lotion and oil' (n = 1192), 'shampoo and conditioner' (n = 968) and 'deodorants' (n = 632). Among cosmetic products labelled to contain at least one of the 26 fragrances, 85.5% and 73.9% contained at least two and at least three of the 26 fragrances, respectively. Linalool (49.5%) and limonene (48.5%) were labelled most often among all investigated products. Hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC/Lyral^® ) was found in 13.5% of deodorants. Six of the 26 fragrance substances were labelled on less than one per cent of all products, including the natural extracts Evernia furfuracea (tree moss) and Evernia prunastri (oak moss). A total of 329 (5.9%) products had one or more of the 26 fragrance substances labelled but did not have 'parfum/fragrance/aroma' listed on the label.

CONCLUSIONS

Consumers are widely exposed to, often multiple, well-established fragrance contact allergens through various cosmetic products intended for daily use. Several fragrance substances that are common causes of contact allergy were rarely labelled in this large sample of cosmetic products.

Contact sensitization to limonene and linalool hydroperoxides in Spain: a GEIDAC* prospective study

BACKGROUND

Limonene and linalool are common fragrance terpenes widely used in cosmetic, household and hygiene products. Their primary oxidation products formed after air exposure, the hydroperoxides, have been recognized as important contact haptens.

OBJECTIVES

To investigate the prevalence of contact allergy to hydroperoxides of limonene (Lim-OOHs) and hydroperoxides of linalool (Lin-OOHs) in Spain, and to define the optimal concentration for screening in consecutive patients.

METHODS

Three different concentrations of Lim-OOHs (0.1%, 0.2% and 0.3% pet.) and Lin-OOHs (0.25%, 0.5% and 1.0% pet.) were simultaneously tested in 3639 consecutive patients at 22 departments of dermatology in Spain.

RESULTS

Lim-OOHs at 0.1%, 0.2% and 0.3% yielded positive patch test reactions in 1.4%, 3.4% and 5.1% of the tested patients, respectively; and Lin-OOHs at 0.25%, 0.5% and 1.0% yielded positive reactions in 1.3%, 2.9% and 4.9% of the tested patients, respectively. Few irritant (1.5-1.9%) and doubtful reactions (0.4-0.5%) to both terpene hydroperoxides were registered at the highest concentrations tested.

CONCLUSIONS

Lim-OOHs and Lin-OOHs can be considered as common causes of contact allergy, and their inclusion in an extended baseline patch test series therefore seems to be appropriate. The patch test preparations of Lim-OOHs 0.3% pet. and Lin-OOHs 1.0% pet. are useful tools for screening of contact sensitization.

Can contact allergy to p-phenylenediamine explain the high rates of terpene hydroperoxide allergy? - An epidemiological study based on consecutive patch test results

BACKGROUND

Contact allergy to linalool hydroperoxides (Lin-OOHs) and limonene hydroperoxides (Lim-OOHs) is common. Similarly to what occurs with the terpene hydroperoxides, reactive intermediates formed from p-phenylenediamine (PPD) can cause oxidative modifications of tryptophan residues on proteins in mechanistic studies.

OBJECTIVES

To test the hypothesis that patients sensitized to PPD are at increased risk of concomitant reactivity to either of the terpene hydroperoxides, owing to a 'common pathway' of skin protein oxidation.

METHODS

A database study of consecutively patch tested eczema patients (n = 3843) from 2012 to 2015, tested concomitantly with PPD, Lim-OOHs and Lin-OOHs, was performed. Associations were examined by level of concordance and odds ratios (ORs) adjusted for age, sex, and contact allergy to fragrance mix I and fragrance mix II.

RESULTS

Concomitant reactions to PPD were seen in 2.2% of Lim-OOH-positive patients and in 4.9% of Lin-OOH-positive patients. Neither proportion was higher than expected by chance. No association existed between PPD and Lim-OOH patch test reactivity. In a multiple logistic regression analysis, PPD allergy was associated with an insignificantly increased risk (OR 2.11, 95%CI:0.92-4.80) of a positive patch test reaction to Lin-OOHs.

CONCLUSIONS

PPD sensitization cannot explain the high rates of sensitization to Lin-OOHs and/or Lim-OOHs. Contact allergy to oxidized linalool is more strongly associated with fragrance allergy than with PPD allergy.

Oxidized limonene and oxidized linalool - concomitant contact allergy to common fragrance terpenes

BACKGROUND

Limonene and linalool are common fragrance terpenes. Both oxidized R-limonene and oxidized linalool have recently been patch tested in an international setting, showing contact allergy in 5.2% and 6.9% of dermatitis patients, respectively.

OBJECTIVE

To investigate concomitant reactions between oxidized R-limonene and oxidized linalool in consecutive dermatitis patients.

METHODS

Oxidized R-limonene 3.0% (containing limonene hydroperoxides 0.33%) and oxidized linalool 6% (linalool hydroperoxides 1%) in petrolatum were tested in 2900 consecutive dermatitis patients in Australia, Denmark, Singapore, Spain, Sweden, and the United Kingdom.

RESULTS

A total of 281 patients reacted to either oxidized R-limonene or oxidized linalool. Of these, 25% had concomitant reactions to both compounds, whereas 29% reacted only to oxidized R-limonene and 46% only to oxidized linalool. Of the 152 patients reacting to oxidized R-limonene, 46% reacted to oxidized linalool, whereas 35% of the 200 patients reacting to oxidized linalool also reacted to oxidized R-limonene.

CONCLUSIONS

The majority of the patients (75%) reacted to only one of the oxidation mixtures, thus supporting the specificity of the reactions. The concomitant reactions to the two fragrance allergens suggest multiple sensitizations, which most likely reflect the exposure to the different fragrance materials in various types of consumer products. This is in accordance with what is generally seen for patch test reactions to fragrance materials.

Severe Photo-oxidative Injury from Over-the-Counter Skin Moisturizer: A Child Abuse Mimic

BACKGROUND

The cutaneous manifestations of pathological conditions have been described to mirror findings commonly associated with child abuse. Although it is important for clinicians to report suspected abuse, vigilance is required to detect conditions that mimic abuse. Phytophotodermatitis, a phototoxic reaction to furocoumarin-containing plants, is a well-described mimicker of nonaccidental trauma. However, non-furocoumarin-containing chemicals may cause similar presentations through a process called auto-oxidation. Typically, these chemical reactions occur as a result of aero-oxidation or, less commonly, photo-oxidation.

CASE REPORT

We report the first pediatric case of photo-oxidative contact dermatitis from an over-the-counter skin moisturizer. A 12-month-old Hispanic boy presented to the Emergency Department with an apparent scald burn over his anterior chest and left shoulder. Given the lack of apparent cause, a nonaccidental injury was suspected. He was admitted to the pediatric service under the consult of Dermatology and the child maltreatment team. Further history and clinical progression strongly suggested a photo-oxidation reaction from chemical components in a widely available over-the-counter skin moisturizer. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case highlights an infrequently reported cause of pediatric contact dermatitis: a photo-oxidative reaction to chemical components in skin moisturizer. It is important for the clinician to be able to differentiate injuries secondary to nonaccidental trauma from conditions that mirror their presentation. The clinical features of this case mimicked child maltreatment and underscore the importance of an interdisciplinary team approach in the care of these children.