Joint publication with dōTERRA: Skin Sensitization potency assessment of Essential Oils



Advancing Skin Sensitization potency assessment for Essential Oils

Comparative analysis of a component-based prediction model, GARDskin Dose-Response assay, and the Local Lymph Node Assay (LLNA)

A new joint article by researchers from dōTERRA and SenzaGen has been published in Toxics, providing new peer-reviewed evidence supporting the applicability of GARD®skin Dose-Response for quantitative skin sensitization potency assessment of Essential Oils, a representative class of Natural Complex Substances (NCS).

The study addresses a key gap in non-animal skin sensitization testing: the quantitative potency assessment of complex mixtures. Results demonstrate strong overall concordance between GARD®skin Dose-Response and historical LLNA data, supporting the use of New Approach Methodologies (NAMs) to derive Points of Departure (PoDs) for quantitative skin sensitization risk assessment of complex mixtures.

About the study

Eight well-studied Essential Oils were evaluated using two non-animal approaches and benchmarked against historical LLNA data:

  • GARD®skin Dose-Response: a genomics-based assay that extends the standard GARDskin OECD 442E methodology to enable quantitative skin sensitization potency assessment.
  • Component-based Prediction (CP) model: a computational approach using constituent composition and known sensitization potency data to estimate mixture potency.

Key findings:

  • Confirmed applicability of GARD®skin Dose-Response to Essential Oils for quantitative potency assessment.
  • Strong overall concordance across all three approaches, indicating comparable potency estimates.
  • GARD®-derived potency values generally aligned with historical LLNA data, supporting the method’s relevance for skin sensitization risk assessment.

Together, these findings provide further evidence supporting the use of non-animal approaches for quantitative skin sensitization risk assessment of complex mixtures. 

Dawson, Joseph T., Tim Lindberg, Prabodh Satyal, Ambika Poudel, Dakota T. Carter, Sara A. Shah, and Cécile Bascoul. 2026. 
"Comparative Analysis of Test Methods for Predicting Dermal Sensitization Potency in Essential Oils: A Component-Based Prediction Model, GARDskin Dose–Response Assay, and Local Lymph Node Assay"
Toxics 14, no. 9: 800. https://doi.org/10.3390/toxics14090800

Keywords

Skin sensitization; risk assessment; essential oils; mixtures; non-animal methods; new approach methodologies (NAMs); component-based prediction; GARDskin Dose-Response; local lymph node assay; comparative analysis


Abstract

The dose–response adaptation of the genomic allergen rapid detection for skin sensitizers (GARDskin DR) assay is a non-animal method for predicting sensitization potency. This proof-of-concept comparative analysis evaluates outputs from a component-based prediction model (CP), GARDskin DR, and historical local lymph node assays (LLNA), exploring the applicability of CP and GARDskin DR for evaluating the no-expected-sensitization induction level (NESIL) potencies of essential oils.

Eight well-studied essential oils were selected: cedarwood, cinnamon bark, clove bud, geranium, lavender, lemongrass, spearmint, and tea tree oils. Each underwent GARDskin DR as well as GC–MS, from which CP model outputs were derived. GARDskin DR, CP, and LLNA outputs were compared graphically and using preliminary descriptive statistics.

Results show overall statistical concordance in material ranking between methods (Kendall’s W = 0.857, p = 0.017). Bland–Altman log-transformed bias and limits of agreement show numerically higher NESILCP compared to corresponding NESILGARD and NESILLLNA, but sensitivity analysis shows this finding is statistically sensitive to geranium oil. Spearman’s rank correlations were significant between NESILCP vs. NESILGARD and NESILLLNA but not between NESILGARD vs. NESILLLNA despite numerical similarity.

Given the small sample, no statistical findings from this study are generalizable and should be interpreted descriptively. However, the NESIL results provide preliminary evidence supporting further evaluation of GARDskin DR and CP for dermal sensitization potency testing of essential oils.

 

SenzaGen’s Newsletter Q2 2026

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SenzaGen Newsletter Q2, 2026

The transition toward non‑animal methods

As regulatory expectations evolve and industry demand for non‑animal testing grows, the need for validated New Approach Methodologies (NAMs) continues to increase.

At ESTIV 2026, SenzaGen and peers explored how validated NAMs are advancing safety assessment, supporting innovation, and shaping the future of toxicology.

Recent EU and US regulatory updates in sensitization

Recent regulatory developments in the EU and U.S. support the shift toward human-relevant, non-animal safety assessment in sensitization testing.

EU: Published a roadmap to phase out animal testing across chemicals, pesticides, medical devices, and other sectors, outlining actions and opportunities, including the potential to fully replace animal testing for skin sensitization by 2029.  Read EU roadmap

EPA (USA): Updated its list of accepted NAMs for the first time since 2021, including OECD TG 497, and introduced a new nomination process to support uptake of alternative methods. Read EPA announcement

Together, these developments highlight the growing need for non-animal testing strategies and quantitative data to support decision-making.

5 typical use scenarios for in vitro skin sensitization potency testing

For professionals in toxicology, regulatory affairs, and product development, reliable potency data enables informed decision‑making early in the development pipeline, helping reduce time to market while ensuring safety and regulatory compliance. Common needs include the following:

1.Establish a Point-of-Departure (PoD) for quantitative risk assessment.
2. Define safe dose levels for materials with expected sensitizing potential.
3.Derive reference NESIL values to support confirmatory human patch testing.
4.Detect low levels of sensitizers in complex cosmetic formulations.
5.Guide formulation optimization decisions.

Explore 3 typical use scenarios

Webinar series: In vitro skin sensitization potency assessment

Our two‑part webinar series highlights practical applications for natural complex substances, novel raw materials with challenging properties, and cosmetic formulations, featuring new data generated in collaboration with dōTERRA, Bayer, The Honest Company, and RIFM.

Now available on demand—watch the full series at your convenience.

Watch recording

DPRA and ADRA (OECD TG 442C) added to our testing services

To support the transition toward NAMs, SenzaGen has added DPRA and ADRA to its service portfolio. These assays complement GARD®skin and support Defined Approaches for Skin Sensitization (DASS) under OECD TG 497.

With test methods covering all key events in the skin sensitization pathway, SenzaGen enables 2o3 DA and ITS strategies tailored to the testing needs:

  • Key Event 1 | OECD TG 442C: DPRA, ADRA
  • Key Event 2 | OECD TG 442D: EpiSensA, KeratinoSens
  • Key Event 3 | OECD TG 442E: GARD®skin
  • In silico predictions

Build a DASS strategy tailored to your substance’s properties

Upcoming events

🌎 Conference: Eurotox 2026 | Vienna, Austria | September 13-16
🌎 Conference: ACT 2026 | San Antonio, TX, USA | November 15-18

A Quick Guide to Respiratory Sensitization Testing

Read more

Swedish TV4: Watch how genomics and machine learning are replacing animal testing in chemical safety

SenzaGen joined Lund University researchers on Swedish TV4 to show how genomics- and machine learning-based methods are transforming the field — delivering faster, more accurate, and human-relevant safety assessment.

See how these approaches can protect human health, meet evolving regulatory demands, and open new opportunities in a market driven by scientific innovation and the global shift away from animal testing.

▶️ Watch interview 

SenzaGen’s Newsletter Q1 2026

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SenzaGen Newsletter Q1, 2026

SOT 2026: Advancing NAMs for skin and respiratory sensitization testing

We had a fantastic time at this year’s SOT meeting in San Diego, connecting with peers, exploring new ideas, and sharing the latest GARD® data on skin and respiratory sensitization from our industry collaborations. Thank you to all our collaborative partners for the outstanding teamwork!

Bayer | Coty | ExxonMobil | GDIT | Haleon | J&J MedTech | Merck

GARD for assessing biopesticides and complex mixtures

Dr Andy Forreryd and Dr Tim Lindberg of SenzaGen presented at SOT symposium sessions, demonstrating how GARD® supports sensitization assessment of biopesticides and complex mixtures.

Respiratory sensitization, protein allergy and medical devices

At SenzaGen’s hosted session, guest speakers from Merck, GDIT, and J&J MedTech shared new GARD® data on respiratory sensitization and ISO 10993-10 compliance for medical devices.

New scientific publication: Quantitative risk assessment of fragrance materials using NAMs

The collaborative work within the International Dialogue for the Evaluation of Allergens (IDEA) has been recently published in Regulatory Toxicology and Pharmacology, presenting new peer-reviewed evidence on the application of New Approach Methodologies (NAMs) in quantitative risk assessment (QRA) of fragrance materials.

The study demonstrates that SenzaGen’s single-assay method GARD®skin Dose-Response, alongside the multiple-assay approaches, delivers PoDs that well align with established human and animal reference potency data, within the expected biological variability.

Read the full article

Establishing safe dose levels for cosmetic ingredients

We are pleased to see another leading global cosmetics company adopt GARD®skin Dose-Response to assess safe use levels of ingredients with potential skin-sensitizing properties. Powered by genomics and machine learning, the assay can be used as a standalone method to support robust, science-driven product development.

Explore 3 typical use scenarios

Upcoming events

🌎 Conference: ITCASS and ERGECD meeting | Strasbourg, France | April 15-17
🎧 Webinar: Advancing NAMs for respiratory sensitization testing-SOT Recap | Apr 22
🌎 Conference: ESTIV Congress | Maastricht, the Netherlands | June 29-July 2

New peer-reviewed publication by IDEA working group: Derivation of a Point of Departure using NAMs for application in Quantitative Risk Assessment of fragrance material

Advancing quantitative NAMs for skin sensitization risk assessment – Collaborative work within IDEA QRA-NAMs Working Group

A new article published in Regulatory Toxicology and Pharmacology presents the outcomes of collaborative work within the International Dialogue for the Evaluation of Allergens (IDEA) QRA-NAMs Working Group.

The publication demonstrates how quantitative New Approach Methodologies (NAMs) can be used to derive Points of Departure (PoDs) for skin sensitization risk assessment.

The study provides peer-reviewed evidence that SenzaGen’s single-assay method GARD®skin Dose-Response, alongside the multiple-assay approaches, delivers PoDs that well align with established human and animal reference potency data, within the expected biological variability.

We are proud that SenzaGen expert Dr Andy Forreryd contributed to the scientific discussions and to the development of the GARD®skin dose-response methodology supporting this work.

About the study

Three quantitative NAM approaches were evaluated across 110 fragrance-related chemicals, benchmarked against the extended IDEA Reference Chemical Potency List (RCPL), which integrates human and animal reference data:
  • Defined approaches combining multiple assays: Regression model and SARA-ICE.
  • GARD®skin Dose-Response: a genomic-based assay evaluated as a stand-alone method.

Scientific and regulatory impact

The work addresses a critical gap in NAM adoption: moving beyond hazard identification to quantitative, decision-relevant risk assessment.

Importantly, the study goes further than method comparison by defining NAM-specific adjustment factors, enabling translation of NAM-PoDs into NESILs for use in Quantitative Risk Assessment (QRA), even for new materials where no legacy data are available. Together, these results provide a scientifically robust and practically applicable framework for implementing quantitative, NAM-based skin sensitization risk assessment and support the continued transition toward animal-free, human-relevant safety assessment.

 

ndreas Natsch, Peter Griem, Amaia Irizar, James Bridges, Matthias Vey, Isabelle Lee, Anne Marie Api, Petra Kern, Ian Kimber,
Derivation of a Point of Departure using NAMs for application in Quantitative Risk Assessment of fragrance materials,
Regulatory Toxicology and Pharmacology,
Volume 167,2026,106052,ISSN 0273-2300,https://doi.org/10.1016/j.yrtph.2026.106052.
https://www.sciencedirect.com/science/article/pii/S0273230026000255

Keywords

Skin sensitization, In vitro testing, Point of departure, Quantitative risk assessment, SARA-ICE, Regression model, GARDskin


Abstract

Skin sensitization is a key endpoint for the safety assessment of topical consumer products. Ingredients with the potential to act as skin sensitizers differ markedly in their threshold for induction but can be used safely if their potency is characterized and exposure remains within an appropriate margin of safety. To this end, the fragrance industry co-developed Quantitative Risk Assessment (QRA) which starts with the No-Expected-Sensitization-Induction-Level (NESIL). Historically, QRA relies on a weight of evidence approach based on animal data, human confirmatory tests and read across. To allow an approach based solely on New Approach Methodologies (NAMs), the International Dialogue for the Evaluation of Allergens (IDEA) initiative, developed an extended Reference Chemical Potency List (RCPL) integrating human and animal data to derive potency values (PV). Here, we use PVs to evaluate the suitability of quantitative NAMs, including Defined Approaches (DAs), to derive a Point-of-Departure (NAM-PoD) for skin sensitization potency assessment. Evaluation of NAM-PoD derived by SARA-ICE DA, Regression DA and GARDskin dose-response assay (GSDR), indicates that the sensitization potency of fragrance chemicals can be reliably predicted using each approach. Through comparison of NAM-PoDs with in vivo human sensitization thresholds, NAM-specific adjustment factors were derived to convert NAM-PoDs into NAM-NESILs for QRA.

 

In Vitro Skin Sensitization Testing of Medical Devices

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SenzaGen’s Newsletter Q4 2025

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SenzaGen Newsletter Q4, 2025

As 2025 draws to a close:
This quarter caps a year of significant progress in advancing non-animal sensitization testing and closing critical data gaps. Combing genomics and machine leaning, GARD® continues to deliver solutions for Safe Dose Levels, Medical Devices, and Challenging Chemicals—driving the shift toward reliable, human-relevant approaches.

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How do you establish safe dose levels for sensitizers during product development?
This question has been front and center at international conferences and webinars this quarter, including ICT and ASCCT, where we’ve shared insights on GARD®skin Dose-Response—a unique method that delivers quantitative sensitization potency data as a stand-alone solution, without combining results from multiple tests.

Applicability to challenging samples
A key discussion point: GARD® can address not only neat chemicals but also complex mixtures like UVCBs, natural extracts, formulations, and hydrophobic materials, making quantitative risk assessment robust for diverse applications.

Quantitative data gain momentum across industries 
Interest is growing across sectors, from cosmetics and chemicals to medical devices and now also high-tech industry, because this approach supports early screening of new ingredients and materials and enables safer, more efficient innovation.

Discover how GARD® enables the derivation of Points of Departure (PoDs) for Quantitative Risk Assessment (QRA), and helps establish safe dose levels for identified sensitizers.

Here’s what you need to know as you plan for 2026: Watch webinar replay
2129 Biocompatibility testing of medical devices

In vitro biocompatibility testing: a cost-efficient, human-relevant and ethical alternative
New data on GARD®skin for Medical Devices was a key highlight at the Biocompatibility Conference in Berlin this November, underscoring how NAMs are gaining traction within ISO 10993. Our experts shared insights on integrating in vitro approaches into efficient biocompatibility strategies.

Interested in the new skin sensitization data? Request our poster to learn more
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UK signals shift to non-animal testing
The UK’s strategy to end regulatory animal testing for skin sensitization, irritation, and eye irritation by 2026 reflects the rapid move toward validated non-animal methods. SenzaGen supports this transition with GARD® for skin sensitization, as well as GLP-compliant skin and eye irritation testing, backed by scientific expertise and personalized guidance.

UK ends animal testing for skin sensitization by 2026 – Read road map
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Expanded lab facilities now open in Lund
Last month, SenzaGen celebrated the opening of our expanded laboratory in Lund. As regulatory initiatives accelerate the shift to non-animal testing, we are ready to support this change with increased capacity, flexibility and innovative solutions. Join us in celebrating this important step enabling the transition to non-animal testing!

Discuss your testing needs with our scientific team
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SenzaGen’s Newsletter Q3 2025

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Safe dose levels for sensitizers, NESIL values for HRIPT, and PoD-based QRA
Skin sensitization potency assessment has been in the spotlight at several toxicology conferences this summer, particularly for fragrances where defining safe dose levels, establishing NESIL values, and applying Point of Departure (PoD)-based Quantitative Risk Assessment (QRA) remain key challenges.

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Webinar: In vitro skin sensitization potency assessment
Our on-demand webinar demonstrates how GARD®skin contributes to these needs with case studies on fragrances, essential oils, botanical extracts, and complex mixtures, in collaboration with Unilever, BIC, Takasago, dōTERRA, IFF, and RIFM.
WATCH THE RECORDING
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OECD TG 497 regulatory update at Eurotox
Thank you to everyone who visited us at this year’s Eurotox and joined the discussions on what GARD®skin’s inclusion in OECD TG 497 means for high performance and extended applicability within the DASS framework. We presented posters and led an interactive session demonstrating applications across complex substance categories such as UVCBs, natural extracts, hydrophobic materials, and formulations.

Connect with our specialists to discuss what this means for your regulatory testing strategy
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GARD® enters final ISO validation

– 100% reproducibility and 97% concordance
At the recent ISO TC 194/WG 8 meeting, SenzaGen presented pre-validation results for GARD®skin Medical Device. The assay achieved 100% reproducibility and 97% concordance with animal data, confirming it is robust and ready for the next step: interlaboratory ring trial validation. This milestone advances NAMs in ISO standards, supporting the shift to non-animal skin sensitization assessments.

Request the poster with full pre-validation data

Upcoming events
🌎 ICT 2025 | Beijing, China | Oct 15-18
🌎 ASCCT 2025 | Gaithersburg, USA | Oct 21-23
🌎 3rd Annual Medical Device Biocompatibility Conference | Berlin | Nov 6-7
🎧 Webinar: How GARDskin fits into OECD TG 497 | Nov 20