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Description of key information

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:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: 2g: Data from handbook or collection data 2e: Study well documented, meets generally accepted scientific principles, acceptable for assessment.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Method: Magnusson and Kligman J. Invest. Dermatol 1969 ; 52 : 268-276
GLP compliance:
no
Type of study:
guinea pig maximisation test
Species:
guinea pig
Strain:
Hartley
Sex:
female
Details on test animals and environmental conditions:
- Strain: Hartley strain albino
- Sex: female (nulliparous and non-gravid)
- Source, age, weight at study initiation: no data
- preliminary study: no data
Route:
intradermal and epicutaneous
Vehicle:
other: see below
Concentration / amount:
- Vehicles:
. for intradermal injection: ethanol/propylene glycol (20/80),
. for the 1st topical application (induction): olive oil,
. for the last topical application (challenge): acetone.

- Tested concentrations:
. For the induction: 2, 20, 200, 2000 and 20000 ppm were tested by intradermal injection. Each one of these concentrations was associated with a 250000 ppm-concentration for the topical application. Moreover, a 0 ppm-concentration was tested too in induction stage (by both injection and topical routes).
. For challenge: each concentration used in induction stage was associated with 5 different concentrations in the challenge stage (topical application): 0, 2, 20, 200, 2000 ppm.

- Test procedure: performed almost in accordance with the original procedure of Magnusson and Kligman. So 21 days after the initial intradermal injection, 0.1 mL aliquots of various concentrations of test substance were applied on the flank of each animal for challenge.

- Challenge exposure duration: 24h

- Rechallenge: no
Route:
epicutaneous, semiocclusive
Vehicle:
other: see below
Concentration / amount:
- Vehicles:
. for intradermal injection: ethanol/propylene glycol (20/80),
. for the 1st topical application (induction): olive oil,
. for the last topical application (challenge): acetone.

- Tested concentrations:
. For the induction: 2, 20, 200, 2000 and 20000 ppm were tested by intradermal injection. Each one of these concentrations was associated with a 250000 ppm-concentration for the topical application. Moreover, a 0 ppm-concentration was tested too in induction stage (by both injection and topical routes).
. For challenge: each concentration used in induction stage was associated with 5 different concentrations in the challenge stage (topical application): 0, 2, 20, 200, 2000 ppm.

- Test procedure: performed almost in accordance with the original procedure of Magnusson and Kligman. So 21 days after the initial intradermal injection, 0.1 mL aliquots of various concentrations of test substance were applied on the flank of each animal for challenge.

- Challenge exposure duration: 24h

- Rechallenge: no
No. of animals per dose:
10 females per dosed groups (35 groups)
. Negative controls (propylene glycol, petrolatum and acetone undiluted): yes, 1 group of 10 animals
Challenge controls:
no
Positive control substance(s):
yes
Remarks:
dinitrochlorobenzene tested at different concentrations
Reading:
1st reading
Group:
negative control
Dose level:
no induction
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
No reaction with all challenge concentrations : 0, 2, 20, 200, 2000 ppm
Remarks on result:
other: Reading: 1st reading. Group: negative control. Dose level: no induction. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: No reaction with all challenge concentrations : 0, 2, 20, 200, 2000 ppm.
Reading:
1st reading
Group:
test group
Dose level:
Intradermal induction = 2 ppm
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
No reaction with all challenge concentrations : 0, 2, 20, 200, 2000 ppm
Remarks on result:
other: Reading: 1st reading. Group: test group. Dose level: Intradermal induction = 2 ppm. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: No reaction with all challenge concentrations : 0, 2, 20, 200, 2000 ppm.
Reading:
1st reading
Group:
test group
Dose level:
Intradermal Induction = 20 ppm
No. with + reactions:
4
Total no. in group:
10
Clinical observations:
Challenge 0 ppm (0/10), 2 ppm (1/10), 20 ppm (2/10), 200ppm (4/10), 2000 ppm (4/10)
Remarks on result:
other: Reading: 1st reading. Group: test group. Dose level: Intradermal Induction = 20 ppm . No with. + reactions: 4.0. Total no. in groups: 10.0. Clinical observations: Challenge 0 ppm (0/10), 2 ppm (1/10), 20 ppm (2/10), 200ppm (4/10), 2000 ppm (4/10).
Reading:
1st reading
Group:
test group
Dose level:
Intradermal induction= 200 ppm
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
Challenge 0 ppm (0/10), 2 ppm (5/10), 20 ppm (8/10), 200ppm (10/10), 2000 ppm (10/10)
Remarks on result:
other: Reading: 1st reading. Group: test group. Dose level: Intradermal induction= 200 ppm. No with. + reactions: 10.0. Total no. in groups: 10.0. Clinical observations: Challenge 0 ppm (0/10), 2 ppm (5/10), 20 ppm (8/10), 200ppm (10/10), 2000 ppm (10/10).
Reading:
1st reading
Group:
test group
Dose level:
Intradermal indution = 2000 ppm
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
Challenge 0 ppm (0/10), 2 ppm (2/10), 20 ppm (8/10), 200ppm (10/10), 2000 ppm (9/10)
Remarks on result:
other: Reading: 1st reading. Group: test group. Dose level: Intradermal indution = 2000 ppm. No with. + reactions: 10.0. Total no. in groups: 10.0. Clinical observations: Challenge 0 ppm (0/10), 2 ppm (2/10), 20 ppm (8/10), 200ppm (10/10), 2000 ppm (9/10).
Reading:
1st reading
Group:
test group
Dose level:
Intradermal induction = 20 000 ppm
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
Challenge 0 ppm (0/10), 2 ppm (9/10), 20 ppm (10/10), 200ppm (9/10), 2000 ppm (9/10)
Remarks on result:
other: see Remark
Remarks:
Reading: 1st reading. Group: test group. Dose level: Intradermal induction = 20 000 ppm. No with. + reactions: 10.0. Total no. in groups: 10.0. Clinical observations: Challenge 0 ppm (0/10), 2 ppm (9/10), 20 ppm (10/10), 200ppm (9/10), 2000 ppm (9/10).
- From the 2 ppm-challenge concentration, the MR as well as the SR,increased with
the challenge concentration, when the induction concentration was held constant.

- The minimum induction concentration of test substance that induces a positive response = 20 ppm (because no positive reactions with any challenge concentrations were found when the induction concentration was 2 ppm).

- The challenge concentration that induces a mean response approximately equal to 1.0 among the animals applied with the highest concentration for induction = 2 ppm.
Interpretation of results:
sensitising
Remarks:
Migrated information
Conclusions:
Positive responses were observed in this Guinea pigs maximalisation test, DPTU is also a skin sensitizer .
Executive summary:

A guinea pigs maximalisation test was performed according to the Magnuson and Kligman method with DPTU.

In induction phase, guinea pigs were exposed by intradermal injection (0, 2, 20, 200, 2000, 20000 ppm of DPTU) and by topical administration (0 or 250 000 ppm of DPTU). In the challenge phase, animals were exposed by topical administration at: 0, 2, 20, 200, 2000 ppm of DPTU.

No effect was observed in the animals which were not induced and/or challenge with DPTU (negative control).
Below 20 ppm ( induction phase), no cutaneous reactions were observed after the challenge application.
In the animals induced by an injection of 20 ppm of DPTU, skin sensitisation was observed in all groups of challenged rats : 1/10 (2 ppm), 2/10 (20 ppm), 4/10 (200 and 2000 ppm).
In the animals induced by an injection of 200 ppm of DPTU, skin sensitisation was observed in all groups of challenged rats : 5/10 (2 ppm), 8/10 (20 ppm), 10/10 (200 and 2000 ppm).
In the animals induced by an injection of 2000 ppm of DPTU, skin sensitisation was observed in all groups of challenged rats : 2/10 (2 ppm), 8/10 (20 ppm), 10/10 (200 ppm) and 9/10 (2000 ppm).
In the animals induced by an injection of 20000 ppm of DPTU, skin sensitisation was observed in all groups of challenged rats : 9/10 (2 ppm), 10/10 (20 ppm), 9/10 (200 ppm) and 9/10 (2000 ppm).

 According this Guinea pigs maximalisation test, DPTU is a skin sensitizer .

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (sensitising)
Additional information:

During the years, the allergenic activity of DPTU has been studied in three different animal models: the murine local lymph node assay (LLNA), the sensitive mouse local lymph node assay (SLNA) and the guinea pigs maximilisation test (GPMT). DPTU was identified as a sensitizer in the GMPT and SLNA but was found to be nonsensitising in the LLNA. This disparity is most probably due to the differences in the administration of the compound in the LLNA versus the SLNA and the GPMT. In the two latter methods, the test compound is administratered intradermally in addition to topical application. Intradermal injections seem to be important to obtain a positive response to DPTU as the penetration of DPTU probably is low when applied topically on intact skin. (Samuelsson K. 2011).

GPMT test (Nakamura 1994) :

A guinea pigs maximalisation test was performed according to the Magnuson and Kligman method with DPTU.

In induction phase, guinea pigs were exposed by intradermal injection (0, 2, 20, 200, 2000, 20000 ppm of DPTU) and by topical administration (0 or 250 000 ppm of DPTU). In the challenge phase, animals were exposed by topical administration at: 0, 2, 20, 200, 2000 ppm of DPTU.

No effect was observed in the animals which were not induced and/or challenge with DPTU (negative control).
Below 20 ppm ( induction phase), no cutaneous reactions were observed after the challenge application.
In the animals induced by an injection of 20 ppm of DPTU, skin sensitisation was observed in all groups of challenged rats : 1/10 (2 ppm), 2/10 (20 ppm), 4/10 (200 and 2000 ppm).
In the animals induced by an injection of 200 ppm of DPTU, skin sensitisation was observed in all groups of challenged rats : 5/10 (2 ppm), 8/10 (20 ppm), 10/10 (200 and 2000 ppm).
In the animals induced by an injection of 2000 ppm of DPTU, skin sensitisation was observed in all groups of challenged rats : 2/10 (2 ppm), 8/10 (20 ppm), 10/10 (200 ppm) and 9/10 (2000 ppm).
In the animals induced by an injection of 20000 ppm of DPTU, skin sensitisation was observed in all groups of challenged rats : 9/10 (2 ppm), 10/10 (20 ppm), 9/10 (200 ppm) and 9/10 (2000 ppm).

According this Guinea pigs maximalisation test, DPTU is a skin sensitizer.

LLNA and SLNA tests (Ikarashi 1994) :

Contact sensitivity of diphenylthiourea (DPTU) was evaluated by a new sensitive mouse lymph node assay (SLNA) and the murine local lymph node assay (LLNA). The results of the SLNA and LLNA were compared with the data of the previous guinea pig maximization test (GPMT).

In the LLNA and SLNA, the sensitizing activity was measured as a function of draining lymph node activation following application of the test chemicals.

DPTU showed negative results in the LLNA. The SLNA successfully detected the sensitivity of this thiourea tested. This result indicated that the SLNA was, in this case, more sensitive than the LLNA for identification of contact allergens.

The predictions of sensitizing potential and the order of the sensitizing capacity of DPTU by the SLNA and the GPMT are very similar.


Migrated from Short description of key information:
DPTU is a human and animal skin sensitizer.
DPTU gave a positive response in a guinea pig maximalisation test (Nakamura 1994) and in a SLNA test (Ikarashi 1994).
DPTU is reported to be an allergen associated with its use as a rubber vulcanisation accelerator and in PVC adhesive tape (Freger 1982, Foussereau 1992).

Justification for selection of skin sensitisation endpoint:
Two reliable studies are available to evaluate the skin sensitizer potential of DPTU. The Nakamura study is selected because showed positive results.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Proposed self-classification

- Regulation (EC) No 1272/2008

Skin sens. 1A (May cause an allergic skin reaction, H317)

Justification: DPTU was positive in the GPMT test (40% at 200 ppm and 2000 ppm of challenge) with an concentration for intradermal induction 0.002% (20 ppm). DPTU is classified in the category 1A according to the Regulation UE n°286/2011 because the incidence sensitised guinea pigs is higher to 30%, and the concentration for intradermal induction is lower to 0.1%.

 

- Directive 67/548/EEC

R43 (May cause sensitisation by skin contact)