Registration Dossier

Administrative data

Description of key information

For the skin sensitisation endpoint, three reliable studies are available : a guinea pigs maximalisation test (Nakamura 1994), a mouse local lymph node assay (LLNA) and a sensitive local node assay on mice (SLNA) (Ikarashi 1994). The results of these studies are conflicting : DETU is showed a sensitisation potential on guinea pigs (GPMT test) and in SLNA test, but not in LLNA test. According to the Ikarashi's publication (1994), SLNA test is more sensitive than LLNA test.
Moreover several cases of allergic contact dermatitis were observed and described in humans (Iuclid section 7.10.4).
Finally, DETU is considered as a skin sensitizer.

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:
comparable to guideline study with acceptable restrictions
Qualifier:
no guideline followed
Principles of method if other than guideline:
Method: Magnusson and Kligman J. Invest. Dermatol 1969 ; 52 : 268-276
GLP compliance:
not specified
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
An old GPMT study and an old LLNA were available in the litterature before REACH registration. No new study were performed on skin sensitisation endpoint to fill the REACH dossier.
Species:
guinea pig
Strain:
Hartley
Sex:
male
Details on test animals and environmental conditions:
no data
Route:
intradermal
Vehicle:
other: olive oil
Concentration / amount:
0, 20, 200, 2000, 20000 ppm
Route:
epicutaneous, open
Vehicle:
other: petrolatum
Concentration / amount:
0, 250000 ppm
No.:
#1
Route:
epicutaneous, open
Vehicle:
other: acetone
Concentration / amount:
0, 2, 20, 200, 2000 ppm
No. of animals per dose:
2-10 per group
Details on study design:
Study protocol :
According to the method of Magnusson and Kligman (Magnusson B, Kligman AM. The identification of contact allergens by animal assay. The guinea pig maximization test. J Invest Dermatol 1969: 52: 268 -276.),a surface of 8 cm² (2x4 cm) was exposed to DETU.

Challenge : On day 22, all the animals received a topical open application of 0.1 ml of the test substance in their right flank (while their left flank received the vehicle).
- Clinical examinations: no
- Mortality: no
- Body weight: no
- Necropsy: no
Positive control substance(s):
yes
Remarks:
but not concomitant
Reading:
1st reading
Group:
negative control
Dose level:
no induction
No. with + reactions:
0
Total no. in group:
7
Clinical observations:
No effects with a challenge of 0 - 0.2 - 2 - 20 - 200 and 2000 ppm
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Group:
test group
Dose level:
Intradermal induction (20 ppm)
No. with + reactions:
0
Total no. in group:
7
Clinical observations:
challenge concentrations =0, 2, 20, 200 or 2000 ppm
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Group:
test group
Dose level:
Intradermal induction (200 ppm)
No. with + reactions:
0
Total no. in group:
7
Clinical observations:
challenge concentrations =0, 2, 20, 200 or 2000 ppm
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Group:
test group
Dose level:
Intradermal induction (2000 ppm)
No. with + reactions:
0
Total no. in group:
7
Clinical observations:
challenge concentrations =0 or 2 ppm
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Group:
test group
Dose level:
Intradermal induction (2000 ppm)
No. with + reactions:
3
Total no. in group:
7
Clinical observations:
Challenge concentration = 20 ppm
Remarks on result:
positive indication of skin sensitisation
Reading:
1st reading
Group:
test group
Dose level:
Intradermal induction (2000 ppm)
No. with + reactions:
4
Total no. in group:
7
Clinical observations:
challenge concentrations = 200 or 2000 ppm
Remarks on result:
positive indication of skin sensitisation
Reading:
1st reading
Group:
test group
Dose level:
Intradermal induction (20 000 ppm)
No. with + reactions:
2
Total no. in group:
7
Clinical observations:
challenge concentrations = 2 ppm
Remarks on result:
positive indication of skin sensitisation
Reading:
1st reading
Group:
test group
Dose level:
Intradermal induction (20 000 ppm)
No. with + reactions:
4
Total no. in group:
7
Clinical observations:
challenge concentrations =20 ppm
Remarks on result:
positive indication of skin sensitisation
Reading:
1st reading
Group:
test group
Dose level:
Intradermal induction (20 000 ppm)
No. with + reactions:
7
Total no. in group:
7
Clinical observations:
challenge concentrations = 200 or 2000 ppm
Remarks on result:
positive indication of skin sensitisation
Reading:
1st reading
Group:
positive control
No. with + reactions:
7
Total no. in group:
7
Remarks on result:
positive indication of skin sensitisation
Below 2000 ppm no cutaneous reactions were observed after the challenge application.
In the animals induced by an injection of 2000 ppm, 3/7 of those challenged by 20 ppm, 4/7 of those challenged by 200 ppm and 4/7 of those challenged by 2000 ppm displayed a positive reaction. Mean response were respectively 0.4, 0.7 and 0.8.
In animals induced by an injection of 20000 ppm, 2/7 of those challenged by 2 ppm, 4/7 of those challenged by 20 ppm, 7/7 of those challenged by 200 ppm and 7/7 of those challenged by 2000 ppm had a positive reaction. 
Mean response were respectively 0.3, 0.6, 1.6 and 2.0.

 

Interpretation of results:
Category 1B (indication of skin sensitising potential) based on GHS criteria
Conclusions:
According this Guinea pigs maximalisation test, DETU is a skin sensitizer .
Executive summary:

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

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

Below 2000 ppm (induction phase) no cutaneous reactions were observed after the challenge application.
In the animals induced by an injection of 2000 ppm, 3/7 of those challenged by 20 ppm, 4/7 of those challenged by 200 ppm and 4/7 of those challenged by 2000 ppm displayed a positive reaction. Mean response were respectively 0.4, 0.7 and 0.8.
In animals induced by an injection of 20000 ppm, 2/7 of those challenged by 2 ppm, 4/7 of those challenged by 20 ppm, 7/7 of those challenged by 200 ppm and 7/7 of those challenged by 2000 ppm had a positive reaction. 
Mean response were respectively 0.3, 0.6, 1.6 and 2.0.

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

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

Key study : Guinea pigs maximalisation test (Nakamura 1994)

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

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

Below 2000 ppm (intradermal induction) no cutaneous reactions were observed after the challenge application. In the animals induced by an intradermal injection of 2000 ppm, 3/7 of those challenged by 20 ppm, 4/7 of those challenged by 200 ppm and 4/7 of those challenged by 2000 ppm displayed a positive reaction. Mean response were respectively 0.4, 0.7 and 0.8 .

In animals induced by an intradermal injection of 20 000 ppm, 2/7 of those challenged by 2 ppm, 4/7 of those challenged by 20 ppm, 7/7 of those challenged by 200 and 2000 ppm had a positive reaction. Mean response were respectively 0.3, 0.6, 1.6 and 2.0 .

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

 

Supporting study (Ikarashi 1994):

Contact sensitivity of diethylthiourea (DETU) 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 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.

DETU was not classified as skin sensitizer in the LLNA. However 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 DETU by the SLNA and the GPMT are very similar.

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. 1B (May cause an allergic skin reaction, H317)

Justification: DETU was positive in the GPMT test (43% at 20 ppm of challenge, and 57% at 200 and 2000 ppm) with an intradermal induction concentration of 0.2% (2000 ppm). DETU is classified in the category 1B according to the Regulation UE n°286/2011 because the incidence sensitised guinea pigs is between 30% and 60%, and the concentration of intradermal induction is between 0.1 and 1%.