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Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
24 November 1987 to 19 December 1987
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1988
Report date:
1988

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.6 (Skin Sensitisation)
Deviations:
no
GLP compliance:
yes
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
Study conducted prior to adoption of LLNA guideline by the OECD.

Test material

Constituent 1
Chemical structure
Reference substance name:
2-isopropyl-9H-thioxanthen-9-one
EC Number:
226-827-9
EC Name:
2-isopropyl-9H-thioxanthen-9-one
Cas Number:
5495-84-1
Molecular formula:
C16H14OS
IUPAC Name:
2-isopropyl-9H-thioxanthen-9-one
Test material form:
solid
Details on test material:
- A mixture of 2-(1-methylethyl)-9H-thioxanthene-9-one and 4-(1-methylethyl).-9H-thioxanthene-9-one.
- Appearance: pale yellow solid

In vivo test system

Test animals

Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Weight at study initiation: 381 to 479 g
- Housing: The guinea-pigs were housed in suspended cages with wire mesh floors.
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: Yes, time period not stated.

ENVIRONMENTAL CONDITIONS
- Temperature: approximately 21 °C
- Humidity: 30 to 70 %
- Air changes: approximately 15 per hour
- Photoperiod: lighting was controlled by means of a time switch to give 12 hours of artificial light in each 24 hour period.

IN-LIFE DATES:
- From: 24 November 1987
- To: 19 December 1987

Study design: in vivo (non-LLNA)

Induction
Route:
other: intradermal and topical
Vehicle:
paraffin oil
Remarks:
(liquid paraffin)
Concentration / amount:
Intradermal: 7.5 % (w/w) 0.1 mL
Topical: 50 % (w/w)
Day(s)/duration:
Topical application was applied one week after the Intradermal injection.
Adequacy of induction:
highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically
Challenge
Route:
other: topical
Vehicle:
paraffin oil
Remarks:
(liquid paraffin)
Concentration / amount:
20 and 10 % (w/w)
Day(s)/duration:
The challenge was performed two weeks after the induction period
Adequacy of challenge:
highest non-irritant concentration
No. of animals per dose:
20 animals in the test group and 10 animals in the control group.
Details on study design:
PRELIMINARY INVESTIGATIONS
- The intradermal and topical irritancy of a range of dilutions of the test material were investigated to identify (a) irritant test substance concentrations suitable for the induction phase of the main study and (b) non-irritant concentrations by the topical route of administration for the challenge phase.
- Concentrations of 7.5 and 50 % w/w in liquid paraffin were the maximum practical concentrations that could be prepared and dosed intradermally and topically respectively.
- The following concentrations of test material were selected: Intradermal injection: 7.5 % w/w in liquid paraffin. Topical application: 50 % w/w in liquid paraffin. Challenge: 20 and 10 % w/w in liquid paraffin.

TREATMENT PROCEDURE
- The method employed in this study for the detection of delayed contact hypersensitivity was the guinea-pig maximisation test described by B. Magnusson and A.M. Kligman (1970).
- The procedure may be considered in two parts, (1) induction, (2) challenge.

INDUCTION
- Intradermal injections: A 4 x 6 cm area of dorsal skin on the scapular region-of the guinea-pig was clipped free of hair with electric clippers. Three pairs of intradermal injections were made simultaneously into the area.
Injectables were prepared as follows:
1. Freund's complete adjuvant was diluted with an equal volume of water-for irrigation.
2. Test material at 7.5 % w/w in liquid paraffin.
3. Test material at 7.5 % w/w in a 50 : 50 mixture of Freund's complete adjuvant and liquid paraffin.
- Topical application: One week after the injections, the same 4 x 6 cm interscapular area was clipped and shaved free of hair. A 2 x 4 cm patch of Whatman No. 3 paper was saturated with the test material at 50 % w/w in liquid paraffin. The patch was placed on the skin and covered by a length of impermeable plastic adhesive tape (5 cm width "Blenderm"). This in turn was firmly secured by elastic adhesive bandage ("Elastoplast" 5 cm width) wound round the torso of the animal and fixed with "Sleek" impervious plastic adhesive tape. The dressing was left in place for 48 hours.
- Control animals: During the induction period the control animals were treated similarly to the test animals with the exception that the test compound was omitted from the intradermal injections and topical application.

CHALLENGE
- The test and control animals were challenged topically two weeks after the induction period using the test material, 20 and 10 % w/w in liquid paraffin.
- Hair was removed by clipping and then shaving from an area on the left flank of each guinea-pig. A 2 x 2 cm patch was saturated with approximately 0.2 mL of test material, 20 % w/w in liquid paraffin and applied to an anterior site on the flank. The test material at 10 % w/w in liquid paraffin was applied in a similar manner to a posterior site. The patches were sealed to the flank for 24 hours using the same materials as for the induction topical application.
- The challenge sites were evaluated 24, 48 and 72 hours after removal of the patches.

SCORING
Reactions were scored according to the following arbitrary scale:
- Erythema and eschar formation:
No erythema = 0
Slight erythema (barely perceptible) = 1
Well-defined erythema = 2
Moderate erythema = 3
Severe erythema (beet redness) to slight eschar formation (injuries in depth) = 4
- Oedema formation:
No oedema = 0
Slight oedema (barely perceptible) = 1
Well-defined oedema (edges of area well-defined by definite raising) = 2
Moderate oedema (raised approximately 1 millimetre) = 3
Severe oedema (raised more than 1 millimetre and extending beyond the area of exposure) = 4
Challenge controls:
- During the induction period the control animals were treated similarly to the test animals with the exception that the test compound was omitted from the intradermal injections and topical application.
-The test and control animals were challenged topically two weeks after the induction period using the test material, 20 and 10 % w/w in liquid paraffin.
Positive control substance(s):
no

Results and discussion

In vivo (non-LLNA)

Resultsopen allclose all
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
10 % (w/w)
No. with + reactions:
11
Total no. in group:
19
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
20 % (w/w)
No. with + reactions:
13
Total no. in group:
19
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
10 % (w/w)
No. with + reactions:
5
Total no. in group:
19
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
20 % (w/w)
No. with + reactions:
5
Total no. in group:
19
Key result
Reading:
other: 3rd reading
Hours after challenge:
72
Group:
test chemical
Dose level:
10 % (w/w)
No. with + reactions:
2
Total no. in group:
18
Key result
Reading:
other: 3rd reading
Hours after challenge:
72
Group:
test chemical
Dose level:
20 % (w/w)
No. with + reactions:
2
Total no. in group:
18
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
10 % (w/w)
No. with + reactions:
1
Total no. in group:
10
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
20 % (w/w)
No. with + reactions:
4
Total no. in group:
10
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
10 % (w/w)
No. with + reactions:
0
Total no. in group:
10
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
20 % (w/w)
No. with + reactions:
1
Total no. in group:
10
Key result
Reading:
other: 3rd reading
Hours after challenge:
72
Group:
negative control
Dose level:
10 % (w/w)
No. with + reactions:
0
Total no. in group:
10
Key result
Reading:
other: 3rd reading
Hours after challenge:
72
Group:
negative control
Dose level:
20 % (w/w)
No. with + reactions:
0
Total no. in group:
10

Any other information on results incl. tables

- The dermal reactions observed in two test animals were more marked than those seen in the controls.

- The dermal response seen in sixteen test animals was similar to that seen in the controls.

- One test animal died prior to the challenge application. Autopsy revealed pale kidneys and free blood in the peritoneal cavity.

- One other test animal removed its own bandage prematurely and was excluded.

Applicant's summary and conclusion

Interpretation of results:
other: Not sensitising in accordance with EU criteria
Conclusions:
Under the conditions of the study, the test material is not considered to be a skin sensitiser.
Executive summary:

A study was conducted to investigate the skin sensitisation potential of the test material in accordance with the standardised guidelines OECD 406 and EU Method B.6.

A preliminary study was performed to determine the intradermal and topical irritancy of a range of dilutions of the test material to identify the irritant test material concentrations suitable for the induction phase of the main study and the non-irritant concentrations by the topical route of administration for the challenge phase.

In the main study for the induction phase intradermal injections were applied on the scapular region-of the guinea-pig which was clipped free of hair with electric clippers. Three pairs of intradermal injections were made simultaneously into the area with a concentration of 7.5 % test material in liquid paraffin. One week after the injections topical application took place on the same 4 x 6 cm interscapular area which was again clipped and shaved free of hair. A 2 x 4 cm patch was saturated with the test material at 50 % w/w in liquid paraffin. The semi-occlusive dressing was left in place for 48 hours. During the induction period the control animals were treated similarly to the test animals with the exception that the test compound was omitted from the intradermal injections and topical application.

The test and control animals were challenged topically two weeks after the induction period using the test material, 20 and 10 % w/w in liquid paraffin applied topically to the same area as during the induction phase but this time at concentrations of 20 % w/w in liquid paraffin applied to an anterior site on the flank and at 10 % w/w in liquid paraffin was applied in a similar manner to a posterior site. The patches were sealed to the flank for 24 hours using the same materials as for the induction topical application. The challenge sites were evaluated 24, 48 and 72 hours after removal of the patches.

The dermal reactions observed in two test animals were more marked than those seen in the controls. The dermal response seen in the other sixteen test animals was similar to that seen in the controls.

Under the conditions of the study, the test material is not considered to be a skin sensitiser.