Registration Dossier

Administrative data

Description of key information

No indication of skin sensitization potential in vivo in a Guinea-Pig Maximization Test (OECD TG 406).

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:
From 13 March 2006 to 13 July 2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
A dermal sensitization study using the Guinea Pig Maximisation Test method according to OECD guideline 406 and GLP (CIT report No. 31450 TSG, 2006), scored as validity 1 according to Klimisch criteria is already available. As this test was carried out before 10 May 2017, and as it meets the requirements set out in Article 13(3), first subparagraph, and Article 13(4), it is considered appropriate to address this standard information requirement.
Furthermore, as indicated in the letter from French Authorities attached in the IUCLID Section 13.2 ("French CA testing program July 2005"), The maximisation test was used instead of the LLNA test due to the low solubility of the test substance.
Species:
guinea pig
Strain:
Hartley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories France, L’Arbresle, France
- Age at study initiation: on day 1, the animals of the main test were 1-2 months old
- Weight at study initiation: 361g ± 14g (males) and 350g ± 12g (females) on day 1
- Housing: housed individually in polycarbonate cages with stainless steel lid (48 cm x 27 cm x 20 cm) equipped with a polypropylene bottle
- Diet: free access to 106 pelleted diet
- Water (e.g. ad libitum): drinking water filtered by a FG Millipore membrane (0.22 micron), ad libitum
- Acclimation period: at least 5 days before the beginning of the study

ENVIRONMENTAL CONDITIONS
- Temperature: 22 ± 2°C
- Humidity: 30 to 70%
- Air changes: approximately 12 cycles/hour of filtered, non-recycled air
- Photoperiod: 12 h/12 h

IN-LIFE DATES: from 15 March 2006 (beginning of the preliminary study) to 15 May 2006 (sacrifice of the animals)
Route:
intradermal
Vehicle:
corn oil
Concentration / amount:
0.1% w/w
Day(s)/duration:
on day 1
Adequacy of induction:
highest concentration used causing mild-to-moderate skin irritation and well-tolerated systemically
Route:
epicutaneous, occlusive
Vehicle:
olive oil
Concentration / amount:
25% w/w
Day(s)/duration:
on day 8 (48 hours)
Adequacy of induction:
non-irritant substance, but skin pre-treated with 10% SDS
No.:
#1
Route:
epicutaneous, occlusive
Vehicle:
olive oil
Concentration / amount:
25% w/w
Day(s)/duration:
on day 22 (24 hours)
Adequacy of challenge:
other: some irritant effect was observed. A second challenge was performed at a lower concentration.
No.:
#2
Route:
epicutaneous, occlusive
Vehicle:
olive oil
Concentration / amount:
10% w/w
Day(s)/duration:
on day 46 (24 hours)
Adequacy of challenge:
highest non-irritant concentration
No. of animals per dose:
group 1 (control group): 5 males, 5 females
group 2 (treated group): 10 males, 10 females
group 3 (additional control group for re-challenge : naïve controls): 5 males, 5 females
Details on study design:
RANGE FINDING TESTS:
A preliminary test was conducted in order to determine the concentrations to be tested in the main study.
- By intradermal route (tested concentrations: 1%, 0.5%, 0.25 and 0.1% (w/w)):
• intradermal injections of the dosage form preparations (0.1 mL) were performed in the interscapular region,
• local reactions were evaluated approximately 24, 48 hours and 6 days after the injections.
- By cutaneous route
Under the conditions of the induction phase (tested concentrations: 25% and 10% (w/w)):
• a filter paper (approximately 8 cm2) was fully-loaded with a dosage form preparation and was then applied to the clipped area of the skin. The filter paper was held in place by means of an occlusive dressing for 48 hours,
• cutaneous reactions were evaluated 24 and 48 hours after removal of the dressing.
- Under the conditions of the challenge phase (tested concentrations: 25% and 10% (w/w)):
• the filter paper of a chamber (Finn Chamber®) was fully-loaded with a dosage form preparation. The chamber was then applied to the clipped area of the skin (one concentration per flank). The chamber was held in place by means of an occlusive dressing for 24 hours,
• cutaneous reactions were evaluated 24 and 48 hours after removal of the dressings.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 2 (one intradermal and one cutaneous)
- type of epicutaneous induction: occlusive
- SLS application: Yes, 0.5 ml SLS at 10% (w/w) in vaseline
- Exposure period: 48 hours (cutaneous induction)
- Test groups:
> injections with 50% (v/v) FCA (Freund complexe adjuvant) in 0.9% NaCl, or test item at 0.1% (w/w) in corn oil, or test item at 0.1% (w/w) in the mixture FCA/0.9% NaCl (50/50, w/w)
> cutaneous application: test item at the concentration of 25% (w/w) in olive oil
- Control group:
> injections with 50% (v/v) FCA in 0.9% NaCl, or vehicle (corn oil), or vehicle at 50% (w/v) in a mixture FCA/0.9% NaCl (50/50, v/v)
> cutaneous application: vehicle alone
- Site: the interscapular region of the animals
- Frequency of applications: not applicable
- Duration: 8 days (total duration of induction period)
- Concentrations: 0.1% (w/w) in corn oil (intradermal), 25% w/w in olive oil (epidermal)

B. CHALLENGE EXPOSURE
- No. of exposures: 2
- Day(s) of challenge: day 22 and day 46
- Exposure period: 24 hours
- Test groups: The filter paper of a chamber (Finn Chamber®) was fully-loaded with the test item at the concentration of 25% (w/w, first challenge) or 10% (w/w, 2nd challenge) in vehicle and was then applied to a shaved area of the skin of the posterior right flank of all animals. The vehicle was applied under the same experimental conditions to the skin of the posterior left flank.
- Control group: The filter paper of a chamber (Finn Chamber®) was fully-loaded with the test item at the concentration of 25% (w/w, first challenge) or 10% (w/w, 2nd challenge) in vehicle and was then applied to a shaved area of the skin of the posterior right flank of all animals. The vehicle was applied under the same experimental conditions to the skin of the posterior left flank.
- Site: Posterior right flank (test substance), posterior left flank (control) in the first challenge. . Median left flank (test substance), median right flank (controls) in the second challenge
- Concentrations: 25% (w/w, first challenge),or 10% (w/w), second challenge in vehicle (olive oil) (right flank), vehicle alone (left flank)
- Evaluation: 24 and 48 hours after patch removal

OTHER:
Macroscopic dermal reactions (erythema and edema) were graded using the following scale:
No reaction -> 0
Slight erythema -> 1
Moderate erythema -> 2
Sever erythema -> 3

The animals were observed at least once a day during the study in order to check for clinical signs and mortality.
Weight of the animals of the controls groups and treated group were recorded at the beginning of the study and then, on day 25 and on the last day of the study (day 49).
Challenge controls:
Vehicle controls on the same animals (left flanks) + Control group (no contact with test substance during induction phase)
Positive control substance(s):
yes
Remarks:
mercaptobenzothiazole (CAS No 149-30-4)
Positive control results:
Mercaptobenzothiazole was not included in the study but is regularly tested by the laboratory under the same conditions.
Based on the findings, the sensitivity of the guinea-pigs strain from the same source is considered satisfactory.
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
0 (vehicle alone, left flank)
No. with + reactions:
0
Total no. in group:
10
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
25% (right flank)
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
grade 1 or 2, beige coloration
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
0 (vehicle alone, left flank)
No. with + reactions:
0
Total no. in group:
10
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
25% (right flank)
No. with + reactions:
3
Total no. in group:
10
Clinical observations:
grade 1, beige coloration
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
0 (vehicle alone, left flank)
No. with + reactions:
0
Total no. in group:
20
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
25% (right flank)
No. with + reactions:
20
Total no. in group:
20
Clinical observations:
grade 1 or 2, beige coloration
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
0 (vehicle alone, left flank)
No. with + reactions:
1
Total no. in group:
20
Clinical observations:
grade 1, dryness of the skin
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
25% (right flank)
No. with + reactions:
13
Total no. in group:
20
Clinical observations:
grade 1, beige coloration, dryness of the skin
Key result
Reading:
rechallenge
Hours after challenge:
24
Group:
negative control
Dose level:
0 (vehicle alone, left flank)
No. with + reactions:
0
Total no. in group:
10
Remarks on result:
other:
Remarks:
control group 1
Key result
Reading:
rechallenge
Hours after challenge:
48
Group:
negative control
Dose level:
0 (vehicle alone, left flank)
No. with + reactions:
0
Total no. in group:
10
Remarks on result:
other:
Remarks:
control group 1
Key result
Reading:
rechallenge
Hours after challenge:
24
Group:
negative control
Dose level:
10% (right flank)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
beige coloration
Remarks on result:
other:
Remarks:
control group 1
Key result
Reading:
rechallenge
Hours after challenge:
48
Group:
negative control
Dose level:
10% (right flank)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
beige coloration
Remarks on result:
other:
Remarks:
control group 1
Key result
Reading:
rechallenge
Hours after challenge:
24
Group:
test chemical
Dose level:
0 (vehicle alone, right flank)
No. with + reactions:
1
Total no. in group:
20
Clinical observations:
grade 1
Key result
Reading:
rechallenge
Hours after challenge:
24
Group:
test chemical
Dose level:
10% (left flank)
No. with + reactions:
3
Total no. in group:
20
Clinical observations:
grade 1, beige coloration
Remarks on result:
no indication of skin sensitisation
Remarks:
but slight irritant effect
Key result
Reading:
rechallenge
Hours after challenge:
48
Group:
test chemical
Dose level:
0 (vehicle alone, right flank)
No. with + reactions:
1
Total no. in group:
20
Clinical observations:
grade 1, dryness of the skin
Key result
Reading:
rechallenge
Hours after challenge:
48
Group:
test chemical
Dose level:
10% (left flank)
No. with + reactions:
1
Total no. in group:
20
Clinical observations:
grade 1, beige coloration, dryness of the skin
Remarks on result:
no indication of skin sensitisation
Key result
Reading:
rechallenge
Hours after challenge:
24
Group:
other: Control group 3
Dose level:
10% (left flank)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
beige coloration
Key result
Reading:
rechallenge
Hours after challenge:
24
Group:
other: Control group 3
Dose level:
0 (vehicle alone, right flank)
No. with + reactions:
0
Total no. in group:
10
Key result
Reading:
rechallenge
Hours after challenge:
48
Group:
other: Control group 3
Dose level:
10% (left flank)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
beige coloration
Key result
Reading:
rechallenge
Hours after challenge:
48
Group:
other: Control group 3
Dose level:
0 (vehicle alone, right flank)
No. with + reactions:
0
Total no. in group:
10
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
positive control
Dose level:
0 (vehicule alone, left flank)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Remarks on result:
no indication of skin sensitisation
Remarks:
Females only. Mercaptobenzothiazole was not included in the study but is regularly tested by the laboratory under the same conditions.
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
positive control
Dose level:
0 (vehicule alone, left flank)
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
none
Remarks on result:
no indication of skin sensitisation
Remarks:
Females only. Mercaptobenzothiazole was not included in the study but is regularly tested by the laboratory under the same conditions.
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
positive control
Dose level:
20% Mercaptobenzothiazole (right flank)
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
Skin effect scores range from 1 to 2, with edema in 5 out of 10 animals.
Remarks on result:
positive indication of skin sensitisation
Remarks:
Females only. Mercaptobenzothiazole was not included in the study but is regularly tested by the laboratory under the same conditions.
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
positive control
Dose level:
20% Mercaptobenzothiazole (right flank)
No. with + reactions:
10
Total no. in group:
10
Clinical observations:
Skin effect score range from 1 to 2, with skin dryness in 9 out of the 10 animals.
Remarks on result:
positive indication of skin sensitisation
Remarks:
Females only. Mercaptobenzothiazole was not included in the study but is regularly tested by the laboratory under the same conditions.

No deaths and no clinical signs were observed during the study.

The body weight change of the treated animals was similar to that of controls.

First challenge:

In the control group 1, no cutaneous reactions were observed on the left flank (vehicle application) of the animals. On the right flank (test item application), a discrete or moderate erythema (grade 1 or 2) was observed in 10/10 and 3/10 animals at the 24 and 48-hour readings, respectively. A beige coloration of the skin was noted in all the animals at both readings. In the treated group 2, on the left flank (vehicle application), a discrete erythema (grade 1), associated with a dryness of the skin, was observed in 1/20 animals at the 48-hour reading. On the right flank (test item application), a discrete or moderate erythema (grade 1 or 2) was noted in 20/20 and 13/20 animals, at the 24 and 48-hour readings, respectively. A dryness of the skin was recorded in 1/20 animals at the 48-hour reading. A beige coloration of the skin was noted in all the animals at both readings. In order to determine whether the observed cutaneous reactions were attributable to delayed contact hypersensitivity or to an irritant effect of the test item, a second challenge application was performed. For this second challenge application, a new control group (group 3), which was free from any previous treatment, was used, and the lower concentration of 10% (w/w) was chosen.

Second challenge:

In the control groups 1 and 3, no cutaneous reactions were observed. A beige coloration of the skin was noted on the left flank (test item application) of all the animals at both readings.

In the treated group 2, on the right flank (vehicle application), a discrete erythema (grade 1), associated with a dryness of the skin at the 48-hour reading, was noted in 1/20 animals at the 24 and 48-hour readings, respectively. On the left flank (test item application), a discrete erythema (grade 1) was noted in 3/20 and 1/20 animals at the 24 and 48-hour readings, respectively. A dryness of the skin was observed in 1/20 animals at the 48-hour reading. A beige coloration of the skin was observed in all the animals at both readings.

As the persistent cutaneous reactions observed in the animals of the treated group 2 were of similar incidence and severity on the left treated flank (test item application) and on the right control flank (vehicle application), they were most probably not attributed to delayed contact hypersensitivity.

Interpretation of results:
GHS criteria not met
Conclusions:
Iron oxide isostearate is not considered to be a skin sensitiser.
Executive summary:

In a dermal sensitization study using the Guinea Pig Maximisation Test method according to OECD guideline 406 and GLP (CIT report No. 31450 TSG), scored as validity 1 according to Klimisch criteria, Iron oxide isostearate was administered to 1 to 2 months old Hartley Guinea pigs (5 controls and 10 treated/sex in the main test).

An induction treatment was carried out as follow:

Day 1, 3 pairs of intradermal injections were performed in the interscapular region of all animals:

- Freund’s Complete Adjuvent (FCA) diluted to 50 % (v/v) with 0.9% NaCl (both groups),

- Test substance at the concentration of 0.1% (w/w) in corn oil (treated group) or vehicle alone (control group),

- Test substance at the concentration of 0.1% (w/w) in corn oil in a mixture of FCA/0.9 % NaCl (50/50, w/w) (treated group) or vehicle at the concentration of 50 % (w/v) in a mixture of FCA/0.9% NaCl (50/50, v/v) (control group).

 

Day 7, the same skin site of both groups was pre-treated with sodium lauryl sulphate before to receive one day later a 48 hours occlusive topical application of the test article at the concentration of 25 % (w/w) in olive oil for treated group or olive oil alone for the control group.

 

The animals of both groups were challenged on day 22 and 46 with a 24 hours cutaneous occlusive application of the test article at the concentration of 25 (1stchallenge) or 10 % (2ndchallenge) (w/w) in olive oil and corn oil alone to the opposite flank.

 

The cutaneous reactions were graded for erythema and oedema 24 and 48 hours after removal of the dressing.

 

 

No deaths and no clinical signs were noted during the study.

After the first challenge application of the test item, in the control group 1, no cutaneous reactions were observed on the left flank (vehicle application) of the animals. On the right flank (test item application), a discrete or moderate erythema was observed in 10/10 and 3/10 animals at the 24 and 48-hour readings, respectively. A beige coloration of the skin was noted in all the animals at both readings.

In the treated group 2, on the left flank (vehicle application), a discrete erythema, associated with a dryness of the skin, was observed in 1/20 animals at the 48-hour reading. On the right flank (test item application), a discrete or moderate erythema was noted in 20/20 and 13/20 animals, at the 24 and 48-hour readings, respectively. A dryness of the skin was recorded in 1/20 animals at the 48-hour reading. A beige coloration of the skin was noted in all the animals at both readings.

After the second challenge application of the test item, in the control groups 1 and 3, no cutaneous reactions were observed. A beige coloration of the skin was noted on the left flank (test item application) of all the animals at both readings.

In the treated group 2, on the right flank (vehicle application), a discrete erythema, associated with a dryness of the skin at the 48-hour reading, was noted in 1/20 animals at the 24 and 48-hour readings, respectively. On the left flank (test item application), a discrete erythema was noted in 3/20 and 1/20 animals at the 24 and 48-hour readings, respectively. A dryness of the skin was observed in 1/20 animals at the 48-hour reading. A beige coloration of the skin was observed in all the animals at both readings.

 

From the results obtained, Iron oxide isostearate is not classified as skin sensitizer according to EU Regulation 1272/2008 (CLP).

 

This skin sensitisation study is classified as acceptable. It does satisfy the guideline requirement for a skin sensitisation study (EC Method B.6) in the guinea pigs.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

A skin sensitization study is available on iron oxide isostearate. This study was performed according to OECD guideline n° 406 and in accordance with GLP. This study was thus scored as validity 1 according to Klimisch criteria and then was selected as the Key study. Further information on skin sensitization potential is also available on both cerium and iron oxide isostearates (Active matter of DPX10 and active matter of DPX11). As these chemicals have been considered as analogues by Competent Authorities (see document "050721-AC-Programme études-DPX13.pdf"attached in section 13.2 and the Read-across justification document attached in this section as well), results of studies performed on both substances are used as supporting evidence.

In a dermal sensitization study using the Guinea Pig Maximisation Test method which was performed according to OECD guideline 406 and in accordance with GLP (CIT report No. 31450 TSG, 2006), Iron oxide isostearate was administered to Hartley Guinea pigs (5 controls/sex (group 1) and 10 treated/sex (Group 2) in the main test). A new control (5 animals/sex, group 3) was added for the 2d challenge.

An induction treatment was carried out on Day 1, using 3 pairs of intradermal injections in the interscapular region of treated animals (group 2) with - the test substance at the concentration of 0.1% (w/w) in corn oil; - the test substance at the concentration of 0.1% (w/w) in corn oil in mixture with Freund’s Complete Adjuvent (FCA)/0.9 % NaCl (50/50, w/w); - FCA alone diluted to 50 % (v/v) with 0.9% NaCl. In the control group 1, the test substance was replaced by the vehicle.

Day 7, the same skin site of both groups was pre-treated with sodium lauryl sulphate before to receive one day later a 48 hours occlusive topical application of the test article at the concentration of 25 % (w/w) in olive oil for treated group or olive oil alone for the control group.

The animals of both groups were challenged on day 22 and 46 with a 24 hours cutaneous occlusive application of the test article at the concentration of 25 % (w/w) in olive oil (1stchallenge) or 10 % (w/w) in corn oil (w/w) (2ndchallenge) on one flank and with the vehicle only on the opposite flank.

The cutaneous reactions were graded for erythema and oedema 24 and 48 hours after removal of the dressing.

No deaths and no clinical signs were noted during the study.

After the first challenge, in the control groupdiscrete or moderate erythema was observed in 10/10 and 3/10 animals on treated skin site at the 24 and 48-hour readings, respectively, while no cutaneous reactions were observed on the flank receiving the vehicle only.

In the treated group 2, on the left flank (vehicle application), a discrete erythema, associated with a dryness of the skin, was observed in 1/20 animals at the 48-hour reading. On the right flank (test item application), a discrete or moderate erythema was noted in 20/20 and 13/20 animals, at the 24 and 48-hour readings, respectively. A dryness of the skin was recorded in 1/20 animals at the 48-hour reading.

A beige coloration of the skin was noted in all the animals of groups 1 and 2 at both reading times.

After the second challenge application, in the control groups 1 and 3, no cutaneous reactions were observed on both flanks. In the treated group 2, on the flank receiving vehicle only, a discrete erythema, associated with a dryness was noted in 1/20 animals at the 24 and 48-hour readings, respectively. On the flank treated with the test item,, a discrete erythema was noted in 3/20 and 1/20 animals at the 24 and 48-hour readings, respectively. A dryness of the skin was observed in 1/20 animals at the 48-hour reading.

A beige coloration of the skin was noted on the flank receiving test item of all animals of all groups at both reading times.

 

As the persistent cutaneous reactions observed in the animals of the treated group 2 were of similar incidence and severity on the treated flank with the test item and on control flank receiving the vehicle only, they were not attributed to delayed contact hypersensitivity and thus, Iron oxide isostearate was not considered as a skin sensitizer according to EU Regulation 1272/2008 (CLP).

This result is supported by data available on similar substances cerium and iron oxide isostearates (Active matter of DPX10 and Active matter of DPX11):

 In a dermal sensitization study using the Guinea Pig Maximisation Test method performed according to OECD guideline 406 and GLP (CIT report No. 22322 TSG, 2001), scored as validity 1 according to Klimisch criteria, Cerium and iron oxide isostearate (Active matter of DPX10, CAS 753480-32-9) was administered to Hartley Guinea pigs ( 5 controls and 10 treated/sex).

The test was performed in 2 phases:

- a phase of induction in which test item was administered by injections to the treated group at the concentration of 1% (w/w) in the vehicle (corn oil) +/- Freund Complete Adjuvant (FCA) or FCA alone, followed 8 days later by a 48 hours topical application of the test article at the concentration of 10 % (w/w) in the vehicle under an occlusive dressing. The control group received injections and topical application of the vehicle only following the same protocol.

- a phase of challenge (day 22 of the study) in which all animals from treated and control groups received on one flank a 24 hours topical application of the test item at a concentration of 5 % (W/W) in vehicle under an occlusive dressing. The other flank received the vehicle only and serves as a control.

The cutaneous reactions were graded for erythema and oedema 24 and 48 hours after removal of the dressing

Few cutaneous reactions of very low incidence and severity were observed in animals of both groups and sometimes as well on the treated flank as on the control flank. They were attributed to a slight irritant effect of the test substance and/or to a consequence of the treatment procedure but not to delayed contact hypersensitivity.

From the results obtained, Cerium and iron oxide isostearate (Active matter of DPX10) is not considered as a skin sensitizer according to EU criteria.

 

In a dermal sensitization study using the Guinea Pig Maximisation Test method performed according to OECD guideline 406 and GLP (CIT report No. 30801 TSG, 2008), scored as validity 1 according to Klimisch criteria, Cerium and iron oxide isostearate (Active matter of DPX11) was administered to Hartley Guinea pigs (5 controls and 10 treated/sex in the main test). An additional control group n°3 of 5 animals/sex was added to the study on day 35 for the second challenge application.

The test was performed in 2 phases:

- a phase of induction in which test item was administered by injections to the treated group 2 at the concentration of 0,5% (w/w) in the vehicle (corn oil) +/- Freund Complete Adjuvant (FCA) or FCA alone, followed 8 days later by a 48 hours topical application of the test article at the concentration of 50 % (w/w) in the vehicle under an occlusive dressing. The control group 1 received injections and topical application of the vehicle only following the same protocol.

- a phase of challenge (day 22 of the study) in which all animals from treated and control groups received on the right flank a 24 hours topical application of the test item at a concentration of 5 % (w/w) in vehicle under an occlusive dressing. The other flank received the vehicle only and served as a control. Skin reactions were evaluated approximately 24 and 48 hours after removal of the dressing.

As equivocal cutaneous reactions were noted after the first challenge, a second challenge application was performed on day 36 on all the animals of the study (control group 1, treated group 2 and control group 3 (free from any previous treatment).

The test item at the concentration of 2.5% (w/w) in olive oil was applied to the median left flank and the vehicle (olive oil) to the median right flank of animals of the three groups, under the same experimental conditions as for the first challenge application.

No deaths and no systemic clinical signs were noted during the study.

After the first challenge a discrete erythema was observed in 2/10 and 3/10 animals in the treated site of the control group 1 at the 24 and 48-hour readings, respectively while a discrete erythema was observed on the flank receiving the vehicle alone in 1/10 animals at the 48-hour reading. A beige coloration of the skin (due to the test item) was observed in 10/10 and 4/10 animals at the 24 and 48-hour readings, respectively. A dryness of the skin was observed in 1/10 animals at the 48-hour reading.

In the treated group 2, no cutaneous reactions were observed on the left flank (vehicle application). On the right flank (test item application), a discrete or moderate erythema was observed in 8/20 and 7/20 animals at the 24 and 48-hour readings, respectively. A beige coloration of the skin (due to the test item) was observed in 20/20 and 12/20 animals at the 24 and 48-hour readings, respectively.

After the second challenge, in the control group 1, only a dryness of the skin was noted on the flank receiving the vehicle only of 1/10 animals at the 48-hour reading. On the flank receiving the test item , a discrete erythema was observed in 2/10 and 1/10 animals at the 24 and 48-hour readings, respectively. A beige coloration of the skin (due to the test item) was observed in 2/10 animals at the 24-hour reading. A dryness of the skin was noted in 1/10 animals at the 48-hour reading.

In the treated group 2, no cutaneous reactions were noted on the flank receiving the vehicle. On the flank treated with the test item, a discrete erythema was observed in 4/20 and 3/20 animals at the 24 and 48-hour readings, respectively. A beige coloration of the skin (due to the test item) was observed in 2/20 animals at the 24 and 48-hour readings.

In the control group 3, only a dryness of the skin was noted on the right flank (vehicle application) of 1/10 animals at the 48-hour reading. On the left flank (test item application), a discrete erythema was observed in 2/10 and 6/10 animals at the 24 and 48-hour readings, respectively.

After the second challenge application of the test item, as the cutaneous reactions observed on the treated flank of the animals of the treated group 2 were of similar severity when compared to those recorded in the animals of the control groups 1 and 3, and as the reactions observed in control group 3 were observed with a higher incidence than in treated group 2 (60% vs 15%), it was considered that the cutaneous reactions observed in the treated animals should not be attributed to delayed contact hypersensitivity.

Microscopic examination of skin samples were also performed on some animals of the preliminary study. The lesions noted in the treated skin from both male and female (acanthosis, eosinophilic infiltration, hyperkeratosis, erythrocyte extravasation) suggested slight irritation, while minimal irritation was evidenced in the control skin site.

From the results obtained, cerium and iron oxide isostearate (Active matter of DPX11) is not classified as skin sensitizer according to EU Regulation 1272/2008 (CLP).

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

From the results obtained, It can be concluded that Iron oxide isostearate is not classified as skin sensitizer according to EU Regulation 1272/2008 (CLP) and that this conclusion is supported by the results obtained with its analogues cerium and iron oxide isostearates (Active matter of DPX 10 and active matter of DPX11).

No data are available for respiratory sensitisation; therefore no conclusion can be made on the classification of this endpoint.