Tall Oil Fatty Acids, compounds with 2-(2-aminoethoxy) ethanol

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

The experimental start dates were 16 Feb 2016 (OECD) and 23 Feb 2016 (EPA), the experimental completion date was 04 Apr 2016 (OECD) and 01 Apr 2016 (EPA).

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.2600 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

The surface tension of test item prepared at 90 % saturation in water was determined to be 32.0 mN/m at 22.0 ± 0.5°C; literature data suggested LLNA study may give false positive result, thus a confirmatory Buehler test was conducted.

Test material

Test material information

Constituent 1

Reference substance name:

Tall Oil Fatty Acids, compounds with 2-(2-aminoethoxy) ethanol

Molecular formula:

Too complex

IUPAC Name:

Tall Oil Fatty Acids, compounds with 2-(2-aminoethoxy) ethanol

Test material form:

liquid

Details on test material:

- Appearance/ Physical State: light brown slightly viscous liquid
- Storage conditions: room temperature, in the dark

In vivo test system

Test animals

Species:

guinea pig

Strain:

Hartley

Remarks:

Hartley-derived albino guinea pigs

Sex:

male/female

Details on test animals and environmental conditions:

Receipt
On 16 Feb 2016, 44 male and 44 female Hartley-derived albino guinea pigs were received from Charles River Laboratories, Inc., St. Constant, QC. The animals were examined and weighed on the day following receipt.

Justification for Test System and Number of Animals
The Hartley-derived guinea pig was chosen as the animal model for this study as it is an accepted rodent species for preclinical toxicity testing by regulatory agencies.

The total number of animals used in this study was considered to be the minimum required to properly characterize the effects of the test substance. This study was designed such that it did not require an unnecessary number of animals to accomplish its objectives.
At this time, studies in laboratory animals provide the best available basis for extrapolation to humans and are required to support regulatory submissions. Acceptable models which do not use live animals currently do not exist.

Animal Identification
Each animal was identified by a cage card and plastic ear tag.

Environmental Acclimation
The animals were acclimated to their designated housing for at least 7 days before the first day of dosing.

Selection, Assignment, and Disposition of Animals
The animals chosen for study were arbitrarily selected from healthy animals. All animals received a detailed pretest observation prior to dosing. Only healthy animals were chosen for study use.
The male range-finding animals were approximately 5 weeks of age on the day prior to dosing with body weights of 372 grams and 380 grams. The female range-finding animals were approximately 6 weeks of age on the day prior to dosing with body weights of 325 grams and 348 grams.
The male main phase animals were approximately 6 weeks of age on the day prior to Induction 1 dosing with body weights ranging from 343 grams to 481 grams. The female main phase animals were approximately 7 weeks of age on the day prior to Induction 1 dosing with body weights ranging from 337 grams to 424 grams.
The male second range-finding animals were approximately 9 weeks of age on the day prior to dosing with body weights of 510 grams and 561 grams. The female second range-finding animals were approximately 10 weeks of age on the day prior to dosing with body weights of 447 grams and 473 grams.
The male third range-finding animals were approximately 10 weeks of age on the day prior to dosing with body weights of 609 grams and 650 grams. The female third range-finding animals were approximately 11 weeks of age on the day prior to dosing with body weights of 493 grams and 515 grams.
The disposition of all animals was documented in the Study Records.

Husbandry
Housing
The animals were pair housed (2 animals of the same sex and same dosing group together) throughout the study in polycarbonate cages containing direct bedding material. Housing and care were as specified in the USDA Animal Welfare Act (9 CFR, Parts 1, 2, and 3) and as described in the Guide for the Care and Use of Laboratory Animals from the National Research Council.

Environmental Conditions
Temperatures of 70°F to 73°F (21°C to 23°C) with a relative humidity of 40% to 52% were maintained. A 12 hour light/12 hour dark cycle was maintained, except when interrupted for designated procedures. Ten or greater air changes per hour with 100% fresh air (no air recirculation) were maintained in the animal rooms.

Food
PMI Nutrition International Certified Guinea Pig Chow No. 5026 was provided ad libitum throughout the study, except during designated procedures. The feed was analyzed by the supplier for nutritional components and environmental contaminants. Results of the dietary analyses were provided by the supplier and are on file at the Testing Facility. It is considered that there are no known contaminants in the feed that would interfere with the objectives of the study.

Water
Municipal tap water after treatment by reverse osmosis and ultraviolet irradiation was freely available to each animal via an automatic watering system, except during designated procedures. Water bottles were provided when required. The water is analyzed semi-annually for microbial contamination and for total dissolved solids, hardness, and various environmental contaminants. Results of these analyses are maintained on file at the Testing Facility. It is considered that there are no known contaminants in the water that could interfere with the outcome of the study.

Animal Enrichment
Beginning at receipt, guinea pigs were pair housed in solid bottom cages containing direct bedding material. As an alternative, guinea pigs were individually housed in solid bottom cages containing direct bedding material. When individually housed, a hiding comfort device (PVC pipe) was provided. In addition, a timothy hay cube was provided to each animal at least weekly.

Veterinary Care
Veterinary care was available throughout the study. No veterinary examinations were required or medicinal treatments were administered during the study.

Study design: in vivo (non-LLNA)

Induction

Route:

epicutaneous, occlusive

Vehicle:

unchanged (no vehicle)

Concentration / amount:

100%

Day(s)/duration:

once per week, for 3 consecutive weeks

Adequacy of induction:

other: There was a clear demonstration of sensitization potential in the guinea pig based on increasing irritation during induction

Challenge

No.:

#1

Route:

epicutaneous, semiocclusive

Vehicle:

propylene glycol

Remarks:

75% test substance in propylene glycol

Concentration / amount:

Following a 2-week rest period after the end of the Induction, a challenge was performed whereby the 20 test and 10 previously untreated (naïve) challenge control guinea pigs were topically treated with 75% test substance in propylene glycol

Day(s)/duration:

48

Adequacy of challenge:

other: At 48 h dermal scores of 1 or 2 were noted in 20/20 animals. Challenge control animals showed no signs of irritation with scores of 0. Group mean dermal scores were higher in the test animals (1.5 to 1.8) as compared to challenge control animals (0.0).

No. of animals per dose:

In the induction phase, 10 male and 10 female guinea pigs were topically treated
The challenge was performed whereby the 20 test and 10 previously untreated (naïve) challenge control guinea pigs were topically treated

Details on study design:

This study was performed in accordance with the United States Code of Federal Regulations, Title 40, Parts 792: Good Laboratory Practice (GLP) Standards and as accepted by Regulatory Authorities throughout the European Union (OECD Principles of Good Laboratory Practice), and Japan (MAFF and METI), and other countries that are signatories to the OECD Mutual Acceptance of Data Agreement.
Exceptions from the above regulations are listed below.
• Characterization of the test substance was performed by the Sponsor or Sponsor subcontractor according to established SOPs, controls, and approved test methodologies to ensure integrity and validity of the results generated; these analyses were not conducted in compliance with the GLP or Good Manufacturing Practice (GMP) regulations.
• Concentration, stability, and homogeneity of the test substance formulations were not determined in this study.
• Concentration, stability, and homogeneity of the α-Hexylcinnamaldehyde (HCA) formulations were not determined in this study.
This study was conducted in accordance with the procedures described herein. All deviations authorized/acknowledged by the Study Director are documented in the Study Records. The report represents an accurate and complete record of the results obtained.
There were no deviations from the above regulations that affected the overall integrity of the study or the interpretation of the study results and conclusions.

Challenge controls:

Following challenge with 75% test substance in propylene glycol, dermal scores of 1 or 2 were noted in 18/20 test animals at the 24-hour scoring interval. At the 48-hour scoring interval, dermal scores of 1 or 2 were noted in 20/20 test animals. The challenge control animals showed no signs of irritation with scores of 0. Group mean dermal scores were higher in the test animals (1.5 to 1.8) as compared to challenge control animals (0.0).

Positive control substance(s):

yes

Remarks:

α-Hexylcinnamaldehyde (HCA)

Results and discussion

Positive control results:

The results of the HCA positive control study demonstrated that a valid test was performed and indicated that the test design would detect potential contact sensitizers.

In vivo (non-LLNA)

Results

Results 1

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

75%

No. with + reactions:

18

Total no. in group:

20

Clinical observations:

Following challenge with 75% test substance in propylene glycol, dermal scores of 1 or 2 were noted in 18/20 test animals at the 24-hour scoring interval.

Remarks on result:

positive indication of skin sensitisation

Remarks:

Based on the results of this study, the test substance is considered to be a contact sensitizer in guinea pigs. The criterion for sensitization (dermal scores ≥ 1 in at least 15% of the test animals) was met at challenge as 80% of the test animals responded with a dermal score of 2.

Results 2

Key result

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

75%

No. with + reactions:

20

Total no. in group:

20

Clinical observations:

Following challenge with 75% test substance in propylene glycol, at the 48-hour scoring interval, dermal scores of 1 or 2 were noted in 20/20 test animals.

Remarks on result:

positive indication of skin sensitisation

Remarks:

Based on the results of this study, the test substance is considered to be a contact sensitizer in guinea pigs. The criterion for sensitization (dermal scores ≥ 1 in at least 15% of the test animals) was met at challenge as 80% of the test animals responded with a dermal score of 2.

Any other information on results incl. tables

RESULTS

Mortality

No mortality occurred during the study.

Range-Finding Phases

(Table 1, Table 2, and Table 3)

Based on the initial range-finding phase, the 100% as received concentration was considered appropriate for conducting the induction phase based on ± (slight patchy erythema) scores through 48 hours. During induction, irritation was observed at the 100% concentration; therefore, prior to challenge, a second range-finding phase was conducted by repeating the 75%, 50%, and 25% concentrations with the addition of a 12.5% concentration. The second range‑finding phase produced increased dermal irritation (±, 1, and 2 erythema scores) at the lower concentrations with only 1 animal showing an erythema score of 1 at the 75% concentration. Based on these results, a third range-finding phase was added at the same concentrations as the second range-finding phase to assess the variability between the first and second range-finding phase results. For the third range-finding phase, the test substance was warmed in an attempt to produce a more homogeneous bulk test substance prior to removal for dilution. The third range-finding phase produced erythema scores of ± at all 3 concentrations and it was determined that the 75% concentration was appropriate as the highest non-irritating concentration for the challenge phase.

Table 1

Topical range finding data

GROUP	ANIMAL NO./SEX BODY WEIGHT (G)	RANGE-FINDING DERMAL SCORES
		100%^a		75%^b		50%^b		25%^b
		24 HOURS	48 HOURS	24 HOURS	48 HOURS	24 HOURS	48 HOURS	24 HOURS	48 HOURS
RANGE-FINDING	6064/M	±	±	0	0	0	0	0	0
	(380)
	6065/M	±	±	0	0	0	0	0	0
	(372)
	6066/F	0	±	0	0	0	0	0	0
	(348)
	6067/F	0	0	0	0	0	0	0	0
	(325)
^aAS RECEIVED. ^bTHE VEHICLE USED WAS PROPYLENE GLYCOL.

Table 2                                                                
Second Topical Range-Finding Data

GROUP	ANIMAL NO./SEX BODY WEIGHT (G)	SECOND RANGE-FINDING DERMAL SCORES
		75%^a		50%^a		25^a		12.5^a
		24 HOURS	48 HOURS	24 HOURS	48 HOURS	24 HOURS	48 HOURS	24 HOURS	48 HOURS
SECOND RANGE-FINDING	6022/M	1	1	2	0	2	2	2	2
	(510)
	6023/M	0	0	1	1	1	1	1	1
	(561)
	6108/F	0	0	1	1	0	0	1	1
	(447)
	6109/F	0	0	±	±	±	±	0	1
	(473)
^aTHE VEHICLE USED WAS PROPYLENE GLYCOL.

Table 3                                                                
Third Topical Range-Finding Data

GROUP	ANIMAL NO./SEX BODY WEIGHT (G)	THIRD RANGE-FINDING DERMAL SCORES
		75%^a		50%^a		25^a		12.5^a
		24 HOURS	48 HOURS	24 HOURS	48 HOURS	24 HOURS	48 HOURS	24 HOURS	48 HOURS
THIRD RANGE-FINDING	6062/M	0	0	0	0	±	0	±	0
	(609)
	6063/M	±	0	0	0	±	0	±	±
	(650)
	6106/F	0	0	±	0	±	0	0	0
	(515)
	6107/F	0	0	0	0	0	0	0	0
	(493)
^aTHE VEHICLE USED WAS PROPYLENE GLYCOL.

Induction Phase

(Table 4)

Dermal scores of ± (slight patchy erythema) or 1 (slight, but confluent or moderate patchy erythema) were present at Induction 1 for all test animals. One animal (male Animal No. 6025) had an erythema score of 0 during Induction 2, while all others had erythema scores of 1 or 2 with 3 animals also showing signs of very slight edema. By Induction 3, male Animal No. 6025 had an erythema score of 1 with all others showing signs of erythema 2 or maximized erythema grade 3 (notable dermal lesions). Additional dermal irritation was observed consisting of blanching, eschar, and/or edema for the test animals.

Table 4                                                                
Individual Induction Data

GROUP	ANIMAL NO./SEX	DERMAL SCORES
		INDUCTION 1		INDUCTION 2		INDUCTION 3
		100%^a		100%^a		100%^a
		24 HOURS	48 HOURS	24 HOURS	48 HOURS	24 HOURS	48 HOURS
TEST	6024/M	1	1	1	1	M-3^BLA-2, ED-2	2^BLA-1, ED-1
	6025/M	1	1	0	0	1	1
	6026/M	1	1	2^ED-1	2^ED-1	M-3^BLA-3, ED-2	M-3^BLA-1, ED-2, ES-2
	6027/M	1	1	2^ED-1	2^ED-1	M-3^BLA-3, ED-2	M-3^BLA-3, ED-2
	6028/M	1	1	2	2	2^ES-1, BLA-1, ED-2	M-3^ED-2, ES-3
	6029/M	1	1	2	2	2	2^ED-1
	6030/M	1	1	2	2	M-3^BLA-3, ED-2	M-3^ED-2, ES-4
	6031/M	1	±	1	2	2^ED-1	2^ED-1
	6032/M	±	±	2	2	M-3^BLA-2, ED-1	M-3^ED-2, ES-3
	6033/M	1	1	±	±	2^ED-1	M-3^BLA-4, ED-2
	6068/F	1	1	2^ED-1	2^ED-1	2^ED-1, ES-1	M-3^BLA-3, ED-2, ES-1
	6069/F	1	1	2	2	2	2^ED-1
	6070/F	±	±	2	2	M-3^ED-2, ES-3	M-3^ED-3, ES-4
	6071/F	1	1	2	2	M-3^ED-2, ES-3	M-3^ED-2, ES-3
	6072/F	1	1	1	1	2^BLA-1, ED-1	M-3^BLA-2, ED-2
	6073/F	±	±	2	2	M-3^ES-2, BLA-1, ED-2	M-3^ES-3, BLA-1, ED-2
	6074/F	1	1	2	2	M-3^ES-4, ED-2	M-3^ES-4, ED-2
	6075/F	1	1	2	2	M-3^ES-4, ED-2	M-3^ES-4, ED-2
	6076/F	±	±	2	2	M-3^ES-4, ED-3	M-3^ES-4, ED-3
	6077/F	1	1	2	2	2^ES-1, BLA-1, ED-2	M-3^ES-4, ED-3
^aAS RECEIVED.

GROUP	ANIMAL NO./SEX	DERMAL SCORES
		INDUCTION 1		INDUCTION 2		INDUCTION 3
		5.0%^a		5.0%^a		5.0%^a
		24 HOURS	48 HOURS	24 HOURS	48 HOURS	24 HOURS	48 HOURS
HCA TEST	6034/M	±^BLA-1	1^BLA-1	M-3^ES-3	M-3^ES-3	2^BLA-1	2^BLA-1
	6035/M	±	1	M-3^ES-3	M-3^ES-3	2	2^BLA-1
	6036/M	2	2	M-3^ES-2, BLA-1	M-3^ES-2, BLA-1	2^BLA-1, ED-1	2^BLA-1, ED-1
	6037/M	2	2	M-3^ES-3	M-3^ES-3	2^BLA-1, ED-1	2^BLA-1, ED-1
	6038/M	2^BLA-1	2^BLA-1	M-3^ES-3	M-3^ES-3	2	2^BLA-1
	6078/F	2	2^ED-1	M-3^ES-3	M-3^ES-3	2^BLA-1	2^BLA-1
	6079/F	2^BLA-1	2^BLA-1	M-3^ES-3	M-3^ES-3	2	2
	6080/F	2	2	M-3^ES-2	M-3^ES-2	2^BLA-1, ED-1	2^BLA-1, ED-1
	6081/F	1^BLA-1	1^BLA-1	M-3^ES-3	M-3^ES-3	2^BLA-1	2^BLA-1
	6082/F	1	1	M-3^ES-3	M-3^ES-3	2^BLA-1	2^BLA-1
^aTHE VEHICLE USED WAS ETHANOL.

Challenge Phase

(Table 5)

Following challenge with 75% test substance in propylene glycol, dermal scores of 1 or 2 were noted in 18/20 test animals at the 24-hour scoring interval. At the 48-hour scoring interval, dermal scores of 1 or 2 were noted in 20/20 test animals. The challenge control animals showed no signs of irritation with scores of 0. Group mean dermal scores were higher in the test animals (1.5 to 1.8) as compared to challenge control animals (0.0).

Following challenge with 2.5% w/v HCA in acetone, dermal scores of 1 or 2 were noted in 10/10 HCA test animals at the 48-hour scoring interval. Dermal reactions in the HCA control animals were limited to scores of ± in 3/10 at the 24-hour interval and none had irritation (erythema 0) by the 48-hour interval. Group mean dermal scores were higher in the HCA test animals (0.4 to 1.6) compared to the HCA control animals (0.2 and 0.0).

Following challenge with 1.0% w/v HCA in acetone, dermal scores of 1 or 2 were noted in 10/10 HCA test animals at the 48-hour scoring interval. Dermal reactions in the HCA control animals were limited to scores of ± in 4/10 and 1 in 1/10 by the 48-hour interval. Group mean dermal scores were higher in the HCA test animals (0.4 to 1.5) compared to the HCA control animals (0.2 to 0.3).

Table 5                                                                
Individual Challenge Data

GROUP	ANIMAL NO./SEX	DERMAL SCORES
		75%^a
		24 HOURS	48 HOURS
TEST	6024/M	0	1
	6025/M	1	1
	6026/M	2^ED-1	2^ED-1
	6027/M	1	2
	6028/M	2^ED-1	2^ED-1
	6029/M	2^ED-1	2
	6030/M	0	1
	6031/M	1	1
	6032/M	1	2
	6033/M	1	2
	6068/F	2^ED-1	2^ED-1
	6069/F	2^ED-1	2
	6070/F	2^ED-1	2^ED-1
	6071/F	2^ED-1	2^ED-1
	6072/F	2	2
	6073/F	2	2
	6074/F	1	2
	6075/F	2	2
	6076/F	2	2
	6077/F	2	2
	MEAN	1.5	1.8
^aTHE VEHICLE USED WAS PROPYLENE GLYCOL.

GROUP	ANIMAL NO./SEX	DERMAL SCORES
		75%^a
		24 HOURS	48 HOURS
CHALLENGE CONTROL	6039/M	0	0
	6040/M	0	0
	6041/M	0	0
	6042/M	0	0
	6043/M	0	0
	6083/F	0	0
	6084/F	0	0
	6085/F	0	0
	6086/F	0	0
	6087/F	0	0
	MEAN	0	0
^aVEHICLE USED WAS PROPYLENE GLYCOL

GROUP	ANIMAL NO./SEX	DERMAL SCORES
		2.5%^a		1.0^a
		24 HOURS	48 HOURS	24 HOURS	48 HOURS
HCA TEST	6034/M	±	1	±	1
	6035/M	0	2	0	1
	6036/M	0	2	0	2
	6037/M	2	2	2	2
	6038/M	±	2	±	2
	6078/F	0	1	0	1
	6079/F	0	1	0	1
	6080/F	±	2	±	2
	6081/F	0	1	0	1
	6082/F	±	2	±	2
	MEAN	0.4	1.6	0.4	1.5
FOR PURPOSES OF CALCULATION, ± = 0.5. ^aTHE VEHICLE USED WAS ACETONE. GROUP ANIMAL NO./SEX DERMAL SCORES   2.5%^a 1.0^a 24 HOURS 48 HOURS 24 HOURS 48 HOURS     HCA CHALLENGE CONTROL 6054/M 0 0 ± ±     6055/M 0 0 ± 0     6056/M ± 0 ± 0     6057/M 0 0 0 1     6058/M 0 0 0 ±     6098/F ± 0 ± ±     6099/F 0 0 0 0     6100/F 0 0 0 ±     6101/F 0 0 0 0     6102/F ± 0 0 0                   MEAN 0.2 0.0 0.2 0.3     FOR PURPOSES OF CALCULATION, ± = 0.5. ^aTHE VEHICLE USED WAS ACETONE.

Body Weights

(Appendix 4)

No test item - related effects on body weight were observed in the test animals during the study. Weight gain in the animals throughout the study interval was indicative of good health in the test and control animals. 

One test animal (male Animal No. 6032) showed a slight body weight loss (2 grams) between Day 28 and Day 34. The Day 34 body weight was collected in preparation for a rechallenge phase that was not needed based on the study requirements were met.

Appendix 4
Individual Body Weight Data

GROUP	ANIMAL NO./SEX	BODY WEIGHT (G)
		DAY -1	DAY 28	34^a
TEST	6024/M	450	570	603
	6025/M	454	615	641
	6026/M	402	552	582
	6027/M	431	638	663
	6028/M	449	702	740
	6029/M	444	691	730
	6030/M	443	672	710
	6031/M	419	618	652
	6032/M	416	588	586
	6033/M	409	636	654
	6068/F	383	536	566
	6069/F	388	583	607
	6070/F	384	533	538
	6071/F	399	592	616
	6072/F	366	534	555
	6073/F	385	567	604
	6074/F	386	550	559
	6075/F	386	577	618
	6076/F	374	486	498
	6077/F	421	557	591
HCA TEST	6034/M	419	622	-
	6035/M	444	647	-
	6036/M	459	707	-
	6037/M	430	642	-
	6038/M	442	513	-
	6078/F	424	593	-
	6079/F	381	520	-
	6080/F	398	550	-
	6081/F	354	460	-
	6082/F	380	580	-
NOTE: - = NOT APPLICABLE. ^aANIMALS WERE WEIGHED FOR POSSIBLE RECHALLENGE PHASE DOSING.   GROUP ANIMAL NO./SEX BODY WEIGHT (G)     DAY -1 DAY 28 DAY 34^a       CHALLENGE CONTROL 6039/M 438 595 -       6040/M 365 608 -       6041/M 343 612 -       6042/M 468 611 -       6043/M 481 482 -       6083/F 382 554 -       6084/F 375 494 -       6085/F 371 560 -       6086/F 394 516 -       6087/F 400 573 -                       HCA CHALLENGE CONTROL 6054/M 440 708 -       6055/M 464 736 -       6056/M 466 723 -       6057/M 452 774 -       6058/M 402 576 -       6098/F 410 531 -       6099/F 385 538 -       6100/F 337 412 -       6101/F 368 488 -       6102/F 382 582 -                       RECHALLENGE CONTROL^b 6044/M 422 - 638       6045/M 451 - 746       6046/M 451 - 741       6047/M 440 - 715       6048/M 443 - 773       6088/F 389 - 554       6089/F 378 - 551       6090/F 383 - 557       6091/F 379 - 579       6092/F 390 - 603       NOTE: - = NOT APPLICABLE. ^aANIMALS WERE WEIGHED FOR POSSIBLE RECHALLENGE PHASE DOSING. ^bA RECHALLENGE GROUP WAS MAINTAINED ON STUDY, HOWEVER THE RECHALLENGE PROCEDURE WAS NOT REQUIRED AS THE CHALLENGE RESULTS WERE DEFINITIVE. GROUP ANIMAL NO./SEX BODY WEIGHT (G)     DAY -1 DAY 28 DAY 34       SECOND RECHALLENGE CONTROL^a 6049/M 461 - -       6050/M 406 - -       6051/M 450 - -       6052/M 425 - -       6053/M 384 - -       6093/F 383 - -       6094/F 401 - -       6095/F 398 - -       6096/F 394 - -       6097/F 413 - -       NOTE: - = NOT APPLICABLE. ^aA SECOND RECHALLENGE GROUP WAS MAINTAINED ON STUDY, HOWEVER, THE SECOND RECHALLENGE PROCEDURE WAS NOT REQUIRED AS THE CHALLENGE RESULTS WERE DEFINITIVE.

Applicant's summary and conclusion

Interpretation of results:

Category 1 (skin sensitising) based on GHS criteria

Conclusions:

The skin sensitisation potential of the test item was assessed in accordance with OECD Guideline 406. Based on the results of this study, the test substance is considered to be a contact sensitizer in guinea pigs. The criterion for sensitization (dermal scores ≥ 1 in at least 15% of the test animals) was met at challenge as 80% of the test animals responded with a dermal score of 2. There was a clear demonstration of sensitization potential in the guinea pig based on increasing irritation during induction with a similar dermal response at challenge, as would be expected in the guinea pig when sensitized to a test substance. The results of the HCA positive control study demonstrated that a valid test was performed and indicated that the test design would detect potential contact sensitizers.

Executive summary:

The dermal sensitization potential of the test substance was evaluated in Hartley-derived albino guinea pigs. In the induction phase, 10 male and 10 female guinea pigs were topically treated with the test substance, as received,once per week, for 3 consecutive weeks. Following a 2-week rest period, a challenge was performed whereby the 20 test and 10 previously untreated (naïve) challenge control guinea pigs were topically treated with 75% test item in propylene glycol.

An α-Hexylcinnamaldehyde (HCA) positive control group consisting of 10 HCA test and 10 HCA control guinea pigs was included in this study. The animals were treated as above with the HCA test animals receiving 5% w/v HCA in ethanol for induction and 2.5% and 1.0% w/v HCA in acetone for challenge.

Test item

Following challenge with 75%the test item in propylene glycol, dermal scores of 1 or 2 were noted in 18/20 test animals at the 24-hour scoring interval. At the 48-hour scoring interval, dermal scores of 1 or 2 were noted in 20/20 test animals. The challenge control animals showed no signs of irritation with scores of 0. Group mean dermal scores were higher in the test animals (1.5 to 1.8) as compared to challenge control animals (0.0).

α-Hexylcinnamaldehyde (HCA)

Following challenge with 2.5% w/v HCA in acetone, dermal scores of 1 or 2 were noted in 10/10 HCA test animals at the 48-hour scoring interval. Dermal reactions in the HCA control animals were limited to scores of ± in 3/10 at the 24-hour interval and none had irritation (erythema 0) by the 48-hour interval. Group mean dermal scores were higher in the HCA test animals (0.4 to 1.6) compared to the HCA control animals (0.2 and 0.0).

Following challenge with 1.0% w/v HCA in acetone, dermal scores of 1 or 2 were noted in 10/10 HCA test animals at the 48-hour scoring interval. Dermal reactions in the HCA control animals were limited to scores of ± in 4/10 and 1 in 1/10 by the 48-hour interval. Group mean dermal scores were higher in the HCA test animals (0.4 to 1.5) compared to the HCA control animals (0.2 to 0.3).

Conclusion

Based on the results of this study,the test item is considered to be a contact sensitizer in guinea pigs. The criterion for sensitization (dermal scores ≥ 1 in at least 15% of the test animals) was met at challenge as 80% of the test animals responded with a dermal score of 2. There was a clear demonstration of sensitization potential in the guinea pig based on increasing irritation during induction with a similar dermal response at challenge, as would be expected in the guinea pig when sensitized to a test substance. The results of the HCA positive control study demonstrated that a valid test was performed and indicated that the test design would detect potential contact sensitizers.