1H-Pyrazole, 1,4-dimethyl-

Endpoint summary

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP compliant, guideline study, available as unpublished report, no restrictions, fully adequate for assessment

Qualifier:

according to guideline

Guideline:

EU Method B.6 (Skin Sensitisation)

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

.

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles River GmbH – Wiga, Kisslegg, FRG
- Age at study initiation: young adults
- Weight at study initiation: 331 – 373 g
- Housing: five animals housed together in Markolon type IV cages; Granulate Type 3/4 bedding (staubfrei), SSNIFF
- Diet: ad libitum, Kliba Labordiät 341 (Kaninchen-Meerschweinchen-Haltungs-diät), Firma Klingentalmühle AG, Kaiseraugst, Switzerland
- Water: ad libitum, tap water
- Acclimation period: 7 days before beginning of the study

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 24
- Humidity (%): 30 - 70
- Air: fully air-conditioned
- Photoperiod (hrs dark / hrs light): 12/12

Route:

intradermal and epicutaneous

Vehicle:

water

Concentration / amount:

- Intradermal induction: 5%
- Epicutaneous induction: unchanged
- Challenge: 75%

Route:

epicutaneous, occlusive

Vehicle:

water

Concentration / amount:

- Intradermal induction: 5%
- Epicutaneous induction: unchanged
- Challenge: 75%

No. of animals per dose:

- Test material: 10
- Control: 5

Details on study design:

RANGE FINDING TESTS
A: PERCUTANEOUS INDUCTION
- Amount applied: 2 x 2 cm filter paper strips were applied to the skin of the flanks under an occlusive dressing (the bandage consists of rubberized linen patches 4 x 4 cm from Russka, test patch 5 x 5 cm of Idealbinde from Pfälzische Verbandstoff-Fabrik, and Fixomull® Stretch (adhesive fleece) from Beiersdorf AG). The test filter paper strip was soaked in the test substance or test substance formulation; thus, the animals were exposed to about 0.15 g of the test substance resp. the test substance formulation. For detecting a possible influence an irritating effects of previous intradermal treatment with Freund's adjuvant, animals pretreated with Freund's adjuvant / 0.9% aqueous NaCl-solution (1 : 1) each, in the same manner as intradermal induction about 3 weeks prior to the application of the test substance were used.
- Exposure period: 2 times for 24 hours within a period of 96 hours in order to detect non-specific phenomena that are not caused by a sensitization reaction but could possibly be attributed to a shift in the irritation threshold.
- Site of application: flank, respective on the same area
- Number of test animals: 4 per test concentration
- Concentrations: 100, 75, 50, 25%
- Readings: 24 and 48 h after the beginning of application

B: INTRADERMAL INDUCTION
- Amount applied: A) Freund's adjuvant / 0.9% aqueous NaCl-solution (1 :1); B) Substance 5% in 0.9% aqueous NaCl-solution; C) Substance 5% in A)
- Readings: 24h after intradermal induction
- Number of test animals: 2
- Concentrations: 5%

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 2 (day 0 intradermal injections + day 7 epicutaneous exposure)
- A row of six intradermal injections in groups of two per animal was made. These injections were: A) front row: 2 injections each of 0.1 mL Freund's adjuvant without test substance emulsified with 0.9% aqueous NaCl-solution in a ratio of 1:1, B) middle row: 2 injections each of 0.1 mL of the test substance formulation, C) back row: 2 injections each of 0.1 mL Freund's adjuvant/ 0.9% aqueous NaCl-solution (1 : 1) with test substance.
- Epicutaneous exposure: 2 x 4 cm filter paper strips were applied to the skin of the shoulder under an occlusive dressing (the bandage consists of rubberized linen patches 4 x 6 cm from Russka and Fixomull® Stretch (adhesive fleece) from Beiersdorf AG). The filter paper strip was soaked in the test substance; thus, the animals were exposed to about 0.3 g of the test substance.
- Exposure period (epicutaneous): 48 hours
- Control group: The animals were given the same injections (A, B, C) but without test substance, only with the formulating agent. For epicutaneous exposure the control groups were not treated.
- Site: shoulder
- Evaluation: 24 h after intradermal injections, and 48 h after epicutaneous exposure.

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Exposure: 2 x 2 cm filter paper strips were applied to the skin of the flank under an occlusive dressing (the bandage consists of rubberized linen patches 4 x 4 cm from Russka, test patch 5 x 5 cm of Idealbinde from Pfälzische Verbandstoff-Fabrik, and Fixomull® Stretch (adhesive fleece) from Beiersdorf AG). The test filter paper strip was soaked in the test substance formulation. Thus the animals were exposed to about 0.15 g of the test substance formulation.
- Day(s) of challenge: 21
- Exposure period: 24 h
- Site: intact flank
- Evaluation (hr after challenge): 24 and 48 after the removal of the patch

Challenge controls:

Treatment of control group 1 with the test substance formulation (control group 2 remained untreated)

Positive control substance(s):

yes

Remarks:

Alpha-Hexylcinnamaldehyde, techn. 85%

Positive control results:

In a positive control test with Alpha-Hexylcinnamaldehyde, techn. 85%, performed 7 months before this study, in 14 out of 17 animals tested sensitisation was observed.

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

75%

No. with + reactions:

0

Total no. in group:

5

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 75%. No with. + reactions: 0.0. Total no. in groups: 5.0.

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

75%

No. with + reactions:

0

Total no. in group:

5

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 75%. No with. + reactions: 0.0. Total no. in groups: 5.0.

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

75%

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 75%. No with. + reactions: 0.0. Total no. in groups: 10.0.

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

75%

No. with + reactions:

0

Total no. in group:

10

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 75%. No with. + reactions: 0.0. Total no. in groups: 10.0.

PRE-TESTS

- In the pretest after two 24-hour percutaneous occlusive applications within 96 hours, the minimum irritant concentration was found to be the unchanged test substance. The maximum non-irritant concentration ge was found to be a 75% test substance preparation in aqua bidest.

- Due to distinct necrotic skin changes 1% test substance preparations have been chosen for the intradermal induction.

INDUCTION

- After intradermal induction well-defined erythema and slight edema were observed at the injection sites of all control group animais and all test group animals at which only Freund's adjuvant / 0.9% aqueous NaCl-solution (1:1) was applied.

- Injection of 1% test substance preparations in 0.9% aqueous NaCl-solution or in Freund's adjuvant / 0.9% aqueous NaCl-solution (1:1) caused well-defined erythema and slight edema in all test group animals.

- The injection sites of the control group animals, which were applied with 0.9%aqueous NaCl-solution, did not show any skin reactions.

- After percutaneous induction with the unchanged test substance incrustation, partially open (caused by the intradermal induction) was observed in addition to well defined erythema and slight edema in all test group animals.

 

CHALLENGE

The challenge with a 75% test substance preparation in aqua bidest. did not cause any skin reaction in all animals of control group1and the test group.

BODY WEIGHT

The expected body weight gain has generally been observed in the course of the study.

Interpretation of results:

not sensitising

Remarks:

Migrated information

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

Skin

An OECD 406 Guinea pig maximisation study was performed in compliance with GLP. Ten animals were intradermal (5%) and epicutaneous (undiluted) induced with the test substance on day 0 and 7, respectively. The intradermal injections were: A) front row: 2 injections each of 0.1 mL Freund's adjuvant without test substance emulsified with 0.9% aqueous NaCl-solution in a ratio of 1:1, B) middle row: 2 injections each of 0.1 mL of the test substance formulation, C) back row: 2 injections each of 0.1 mL Freund's adjuvant/ 0.9% aqueous NaCl-solution (1 : 1) with test substance. For the epicutaneous induction the animals were exposed to about 0.3 g test substance for 48 hours. On day 21 the animals were epicutaneously challenged for 24 hours to 75% test substance (about 0.15 g). 75% test substance was determined to be the maximum non-irritant concentration in a preliminary test. Challenge controls were performed in parallel, 5 animals per control group. A positive control was performed with alpha-hexylcinnamaldehyde 85%. Both negative and the positive control showed that the results are reliable. Readings were performed 24 and 48 hours after the challenge. No sensitization was observed in all animals. Under the conditions of this test the substance was considered to be not sensitizing. 

Migrated from Short description of key information:
Skin sensitisation: OECD 406, not sensitizing (BASF, 1995)

Justification for selection of skin sensitisation endpoint:
Only study available

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Based on the available information the substance is not classified for skin sensitisation in accordance with EU Classification, Labeling and Packaging of Substances and Mixtures (CLP) Regulation No. 1272/2008.