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Description of key information

GPMT: not sensitising

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
Reference
Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
10 Aug - 28 Sep 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Version / remarks:
adopted Jul 1992
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.2600 (Skin Sensitisation)
Version / remarks:
Mar 2003
Deviations:
not specified
Qualifier:
according to guideline
Guideline:
other: EC No 440/2008, part B. Skin Sensitization: Guinea-Pig Maximization Test (GPMT)
Version / remarks:
May 2008
Deviations:
not specified
Qualifier:
according to guideline
Guideline:
other: JMAFF Guidelines
Version / remarks:
2000
Deviations:
not specified
GLP compliance:
yes
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
The guinea pig maximization test was selected since the available alternative in vitro tests for skin sensitization are not applicable for the test item due to its intrinsic properties. The guinea pig Maximization test was selected as animal test since the test item is a fatty acid and the Local Lymph Node Assay as preferred animal alternative has shown to provide false positive results for fatty acids.
Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River France, L’Arbresle, France
- Microbiological status of animals, when known: SPF
- Age at study initiation: approximately 4 - 5 weeks
- Weight at study initiation: 283 - 330 g
- Housing: Animals were group housed (up to 5 animals of the same sex and same dosing group together) in labeled Noryl cages (Tecniplast; 74 cm x 54 cm x 25 cm height) containing sterilized sawdust as bedding material (Lignocel S 8-15, JRS - J.Rettenmaier & Söhne GmbH + CO. KG, Rosenberg, Germany) equipped with water bottles.
- Diet: Complete maintenance diet for guinea pigs (MS-H, SSNIFF® Spezialdiäten GmbH, Soest, Germany), ad libitum
- Water: tap water, ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 - 23
- Humidity (%): 43 - 73
- Air changes (per hr): ten or greater
- Photoperiod (hrs dark / hrs light): 12/12

- IN-LIFE DATES: From: 10 Aug 2018 To: 28 Sep 2018
Route:
intradermal
Vehicle:
unchanged (no vehicle)
Concentration / amount:
100%
Day(s)/duration:
single injection on Day 1
Adequacy of induction:
non-irritant substance, but skin pre-treated with 10% SDS
Route:
epicutaneous, semiocclusive
Vehicle:
unchanged (no vehicle)
Concentration / amount:
100%
Day(s)/duration:
Applied on Day 7, 48 h
Adequacy of induction:
non-irritant substance, but skin pre-treated with 10% SDS
No.:
#1
Route:
epicutaneous, semiocclusive
Vehicle:
unchanged (no vehicle)
Concentration / amount:
100%
Day(s)/duration:
1 day
Adequacy of challenge:
highest non-irritant concentration
No. of animals per dose:
5 (control) and 10 (treatment group)
Details on study design:
RANGE FINDING TESTS:
To determine a suitable concentration for the intradermal induction in the main study, a series of four test item concentrations (10, 20, 50 and 100%) was selected. A total of 2 female guinea pigs each received two different concentrations (50 and 100%) in duplicate (0.1 mL/site) in the clipped scapular region. The injection sites were assessed for irritation 24 and 48 hours after treatment. The degree of erythema at the injection sites was recorded 24 and 48 h after injection.
To determine a suitable concentration for the epicutaneous induction in the main study, a series of four test item concentrations was tested, the highest concentration being the undiluted test item. Two different concentrations were applied (0.5 mL each per animal to the clipped flank, using Metalline patches (2x3 cm) mounted on Medical tape which were held in place with Micropore tape and subsequently Coban elastic bandage. The animals receiving intradermal injections were treated with the lowest concentrations and two other animals with the highest concentrations. The degree of erythema at the injection sites was recorded 24 and 48 h after injection.
Based on the results, the test item concentration selected for the main study was the undiluted test item for the intradermal and epidermal induction and for the challenge. No signs of irritation were observed to the undiluted test item dosed epidermally and therefore, the test site of all animals of the main study were treated with 10% SDS approximately 24 hours before the epidermal induction, to provoke a mild inflammatory reaction.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 2 (intradermal and epicutaneous, respectively)
- Exposure period: single injection (intradermal) and 48 h (epicutaneous)
- Test groups:
Intradermal (3 pairs of injections):
Injection 1: a 1:1 mixture (v/v) FCA/water
Injection 2: unchanged (100%) test material
Injection 3: unchanged (100%) test material in a 1:1 mixture (v/v) FCA/water
Epicutaneous: the undiluted test substance
- Control group:
Intradermal (3 pairs of injections):
Injection 1: a 1:1 mixture (v/v) FCA/water
Injection 2: corn oil
Injection 3: corn oil in a 1:1 mixture (v/v) FCA/water
Epicutaneous: blank patch
- Site: shoulder region (intradermal and epicutaneous)
- Frequency of applications: Day 0 (intradermal) and Day 7 (epicutaneous)
- Duration: Days 0 - 7
- Concentrations: intradermal and epicutaneous: undiluted test material

B. CHALLENGE EXPOSURE
- No. of exposures: 1 (challenge)
- Day(s) of challenge: 21
- Exposure period: 24 h
- Test groups: test substance in arachis oil BP and test substance only
- Site: one flank (test substance only), other flank (vehicle)
- Concentrations: undiluted test material
- Evaluation: 24 and 48 h after patch removal
Positive control substance(s):
no
Positive control results:
A reliability check is carried out at regular intervals to check the sensitivity of the test system and the reliability of the experimental techniques as used by the testing facility. In this study, performed in July 2017, females of the Dunkin Hartley guinea pig (from Charles River France, L’Arbresle, France) were checked for the sensitivity to alpha-hexylcinnamaldehyde, technical grade.
The skin reactions observed in 10/10 animals in response to the 50% test item concentration in the challenge phase were considered indicative of sensitisation, based on the absence of any response in the control animals. These results lead to a sensitisation rate of 100 percent to the 50% concentration. From these results, it was concluded that the female guinea pig of the Dunkin Hartley strain is an appropriate animal model for the performance of studies designed to evaluate the sensitizing potential of a test item in a Maximization type of test.
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
Induction: undiluted (intradermal + epicutaneous); Challenge: undiluted (epicutaneous)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
Induction: 0% (intradermal + epicutaneous); Challenge: undiluted
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
none
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
Induction: undiluted (intradermal + epicutaneous); Challenge: undiluted (epicutaneous)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
Induction: 0% (intradermal + epicutaneous); Challenge: undiluted
No. with + reactions:
0
Total no. in group:
5
Clinical observations:
none
Group:
positive control
Remarks on result:
positive indication of skin sensitisation

Table 1: Induction readings

Control Animals

Animal Number

Intradermal injections (readings Day 3)

Epidermal exposure
(readings Day 10)

1:1 Mixture of FCA and water for injection

Corn oil

1:1 Mixture of FCA and corn oil

Corn oil

Erythema

Signs of necrosis
(Ø mm)

Erythema

Signs of necrosis
(Ø mm)

Erythema

Signs of necrosis
(Ø mm)

Erythema

Oedema

41

0

 

0

 

0

 

1

0

42

 

5

0

 

0

 

1

0

43

 

2

0

 

0

 

1

0

44

 

2

0

 

0

 

1

0

45

 

3

0

 

0

 

1

0

Experimental Animals

Animal Number

Intradermal injections (readings Day 3)

Epidermal exposure
(readings Day 10)

1:1 Mixture of FCA and water for injection

Undiluted test item

1:1 Mixture of FCA and
undiluted test item

Undiluted test item

Erythema

Signs of necrosis
(Ø mm)

Erythema

Signs of necrosis
(Ø mm)

Erythema

Signs of necrosis
(Ø mm)

Erythema

Oedema

46

 

1

0

 

 

5

1

0

47

1

 

1

 

 

3

2

0

48

1

 

1

 

 

2

2

0

49

1

 

1

 

 

3

1s

0

50

 

3

0

 

 

5

1s

0

51

 

2

0

 

0

 

2s

1

52

 

2

0

 

0

 

1

1

53

 

4

 

2

 

6

1

0

54

1

 

1

 

 

2

2

1

55

 

2

 

3

 

2

1s

1

FCA = Freunds' Complete Adjuvant, s. = Scaliness.

Grading erythema:

0 = No erythema

1 = Slight erythema (barely perceptible)

2 = Well-defined erythema

Grading Oedema:

0 = No oedema

1 = Slight oedema (barely perceptible)

Table 2: Challenge readings

Animal number

Day 24

Day 25

Comments

Undiluted

test item

Vehicle

Undiluted

test item

Vehicle

Control

 

 

 

 

 

41

0

0

0

0

 

42

0

0

0

0

 

43

0

0

0

0

 

44

0

0

0

0

 

45

0

0

0

0

 

Experimental

 

 

 

 

 

46

0

0

0

0

not sensitized

47

0

0

0

0

not sensitized

48

0

0

0

0

not sensitized

49

0

0

0

0

not sensitized

50

0

0

0

0

not sensitized

51

0

0

0

0

not sensitized

52

0

0

0

0

not sensitized

53

0

0

0

0

not sensitized

54

0

0

0

0

not sensitized

55

0

0

0

0

not sensitized

Grading challenge reactions:

0 = No visible change

Interpretation of results:
other: not sensitising according to Regulation (EC) No. 1272/2008
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

A Guinea pig maximisation test was performed with the test substance according to OECD guideline 406 and under GLP conditions (Charles River, 2018). A range-finding study was performed to establish suitable dose levels for the induction and challenge treatments. Based on the results, the test material concentration selected for the main study was the undiluted test item for the intradermal and epidermal induction and for the challenge. No signs of irritation were observed to the undiluted test material dosed epidermally and therefore, the test site of all animals of the main study were treated with 10% SDS approximately 24 hours before the epidermal induction, to provoke a mild inflammatory reaction. In the main study, 10 female Dunkin-Hartley guinea pigs were induced intradermally on Day 0 with the undiluted test substance on both sides of the spine with and without Freund’s Complete Adjuvant (FCA). On day 7, the undiluted test substance was applied to the skin of the animals for 48 hours under semiocclusive conditions. On Day 21, the challenge treatment was performed by topical application of the test substance in undiluted form for 24 hours under semiocclusive conditions. Five animals served as negative controls and were exposed to corn oil according to the same protocol as the treatment animals. Reliability checks were performed with alpha-hexylcinnamaldehyde under the same experimental conditions and indicated the reliability and sensitivity of the animal strain and study. Following the intradermal induction, slight erythema were observed at the injection sites of 4/10 treatment animals (undiluted test material) and none of the control animals (corn oil) on reading Day 3. Slight and well-defined erythema were observed at the injection sites of 10/10 treatment animals (undiluted test material) and 5/5 control animals (corn oil) on the reading Day 10. In addition, 4/10 treatment animals showed slight oedema on the reading Day 10. At the challenge, 0/10 treatment animals and 0/5 control animals showed skin reactions at the challenge site 24 and 48 h after the challenge treatment, indicating that the test substance does not cause skin sensitisation. Under the conditions of this test the test substance is considered to be not sensitising to guinea pigs.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

The available data on skin sensitisation do not meet the classification criteria according to Regulation (EC) No. 1272/2008 and are therefore conclusive but not sufficient for classification.