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Description of key information

In an apparently well conducted GLP study conducted in accordance with OECD 406 (Guinea Pig Maximization), there were no clinical signs and no deaths noted during the study. No cutaneous reactions were observed after the challenge application (de Jouffrey, 1996). The guinea-pigs which were used in a recent study, showed a satisfactory sensitization response in 100% animals using a positive sensitizer.

Migrated from Short description of key information:

In a key study which evaluated the skin sensitization potential of dilauroyl peroxide to guinea pigs using the maximization test, no positive reactions were reported.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Referenceopen allclose all

Endpoint:
skin sensitisation: in vitro
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
an in vitro skin sensitisation study does not need to be conducted because adequate data from an in vivo skin sensitisation study are available
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: Apparently well conducted study
Qualifier:
according to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Deviations:
not specified
GLP compliance:
yes
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
study was conducted with an accepted guideline at the time, before LLNA method was adopted
Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
male/female
Details on test animals and environmental conditions:
Animals
Species and strain: Dunkin-Hartley guinea-pigs.
Reason for this choice: species recommended by the international regulations for sensitization
studies. The strain used has been shown to produce a satisfactory sensitization response using
known positive sensitizers.

Number: 30 animals (15 males and 15 nulliparous and non-pregnant females).
Allocation of the animals to the groups: on day -1, the animals were weighed and randomly
allocated to two groups: a control group 1 consisting of ten animals (five males and
five females) and a treated group 2 consisting of 20 animals (ten males and ten females).
Weight: on day 1, the animals were approximately three months old and had a mean body
weight ± standard deviation of 353 ± 26 g for the males and 339 ± 21 g for the females.
Acclimatization: at least five days before the beginning of the study.
Identification of the animals: ear-tattoo.
Environmental conditions
During the acclimatization period and throughout the study, the conditions in the animal room
were set as follows:
temperature: 21 ± 2°C
relative humidity: 30 to 70%
light/dark cycle: 12 h/12 h
ventilation: about 12 cycles/hour of filtered, non-recycled air.
The temperature and relative humidity were recorded continuously and records retained.
The housing conditions (temperature, relative humidity, light/dark cycle and ventilation) were
checked regularly.
During the acclimatization period and throughout the study, the animals were housed
individually in polycarbonate cages (48 cm x 27 cm x 20 cm) equipped with a polypropylene
bottle.
Dust-free sawdust was provided as litter (SICSA, 92142 Alfortville, France).
Bacteriological analysis of the sawdust and detection of possible contaminants (pesticides,
heavy metals) are performed periodically.
Route:
intradermal
Vehicle:
paraffin oil
Concentration / amount:
Induction (treated group)
intradermal injections: DILAUROYL PEROXIDE at I% (w/w) in paraffin oil.
. topical application: DILAUROYL PEROXIDE at 20% (w/w) in paraffin oil.
Challenge Call groups)
. topical application: DILAUROYL PEROXIDE at 1% (w/w) in paraffin oil.
Route:
epicutaneous, occlusive
Vehicle:
paraffin oil
Concentration / amount:
Induction (treated group)
intradermal injections: DILAUROYL PEROXIDE at I% (w/w) in paraffin oil.
. topical application: DILAUROYL PEROXIDE at 20% (w/w) in paraffin oil.
Challenge Call groups)
. topical application: DILAUROYL PEROXIDE at 1% (w/w) in paraffin oil.
No. of animals per dose:
Thirty guinea-pigs were allocated to two groups: a control group 1 (five males and five females)
and a treated group 2 (ten males and ten females).
Details on study design:
On day 1, in the dorsal region between the shoulders, intradermal injections of Freund's
complete adjuvant mixed with the test substance (treated group) or the vehicle (control group)
were prepared.

On day 8, this same test site was treated by topical application of the test substance (treated
group) or the vehicle (control group) and was covered by an occlusive dressing for 48 hours.

After a rest period of 12 days, all animals of the treated and control groups were challenged by a
topical application of the test substance to the right flank. The left flank served as control and
received the vehicle only.

Test substance and vehicle were maintained under an occlusive dressing for 24 hours. Skin
reactions were evaluated approximately 24 and 48 hours later.

Twenty-four and 48 hours after the challenge application, both flanks of the treated and control
animals were observed in order to evaluate cutaneous reactions, according to the following
scale:
Erythema and eschar formation
· No erythema....................................................................................................................... 0
· Very slight erythema (barely perceptible) ......................................................................1
· Well-defined erythema ......................................................................................................2
· Moderate to severe erythema ..........................................................................................3
· Severe erythema (beet redness) to slight eschar formation (injuries in depth)...... 4
Oedema formation
· No oedema............................................................................................................................ 0
· Very slight oedema (barely perceptible)........................................................................... 1
· Slight oedema (visible swelling with well-defined edges).............................................. 2
· Moderate oedema (visible swelling raised more than I millimetre) ..............................3
· Severe oedema (visible swelling raised more than 1 millimetre and extending
beyond the area of exposure) .............................................................................................4

Any other lesions were noted.

CLINICAL EXAMINATIONS
The animals were observed twice a day during the study in order to check for clinical signs and
mortality.
BODY WEIGHT
The animals were weighed individually on the day of allocation into the groups, on the first day
of the study (day 1), on days 8 and 15 and on the last day of the study.

PATHOLOGY
Necropsy
At the end of the study, all the animals were killed by CO2 inhalation in excess. No necropsy
was performed.

Cutaneous samples
No skin samples were taken.

Microscopic examination
No histological examinations were performed.

The treated animals show a positive reaction if macroscopic cutaneous reactions are clearly
visible (erythema ~ 2) and if the treated animals have a greater intensity or duration of response
than the maximum reaction seen in control animals, or, if macroscopic reactions are confirmed
at microscopic examination as being due to the sensitization process. Sensitization reactions are
characterized at microscopic examination by basal spongiosis, reactional acanthosis of the
epidermis and infiltration of mononucleated cells into the dermis (I).

% of animals Allergenicity Classification
showing a reaction level
o - 8 I very weak
9 - 28 II weak
29 - 64 III moderate
65 - 80 IV strong
81 - 100 V very strong

According to the Commission Directive 93121/E.E.C., when the reactions are positive in at least
30% of the treated animals, the test substance has sensitization properties and the sentence
"R 43: May cause sensitization by skin contact" must be applied.

Challenge controls:
Control groups were challenged by a topical application of the test substance to the right flank.
Positive control substance(s):
yes
Remarks:
2,4-dinitro chlorobenzene
Positive control results:
Under our experimental conditions and according to the Magnusson and Kligman method,
2,4-dinitro chlorobenzene at a concentration of 1% (w/w) induced positive skin sensitization
reactions in 100% of the guinea-pigs.
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
1% in paraffin oil
No. with + reactions:
0
Total no. in group:
20
Clinical observations:
None
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 1% in paraffin oil. No with. + reactions: 0.0. Total no. in groups: 20.0. Clinical observations: None.
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
1% in paraffin oil
No. with + reactions:
0
Total no. in group:
20
Clinical observations:
None
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 1% in paraffin oil. No with. + reactions: 0.0. Total no. in groups: 20.0. Clinical observations: None.
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
1% in paraffin oil
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
None
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 1% in paraffin oil. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: None.
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
Dose level:
1% in paraffin oil
No. with + reactions:
0
Total no. in group:
10
Clinical observations:
None
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 1% in paraffin oil. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: None.
Reading:
1st reading
Hours after challenge:
24
Group:
positive control
Dose level:
1%
No. with + reactions:
20
Total no. in group:
20
Clinical observations:
None reported
Remarks on result:
other: Reading: 1st reading. . Hours after challenge: 24.0. Group: positive control. Dose level: 1% . No with. + reactions: 20.0. Total no. in groups: 20.0. Clinical observations: None reported.
Reading:
2nd reading
Hours after challenge:
48
Group:
positive control
Dose level:
1%
No. with + reactions:
20
Total no. in group:
20
Clinical observations:
None reported
Remarks on result:
other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: positive control. Dose level: 1%. No with. + reactions: 20.0. Total no. in groups: 20.0. Clinical observations: None reported.
Interpretation of results:
GHS criteria not met
Conclusions:
Under the experimental conditions and according to the maximization method of Magnusson
and Kligman, no cutaneous reactions attributable to the sensitization potential of the test
substance DILAUROYL PEROXIDE were observed in guinea-pigs.
Executive summary:

The potential of the test substance DILAUROYL PEROXIDE to induce delayed contact hypersensitivity was evaluated in guinea-pigs according to the maximization method of Magnusson and Kligman and to O.E.C.D. (No. 406, 17th July 1992) and E.C. (92/69/E.E.C., B6) guidelines. The study was conducted in compliance with the principles of Good Laboratory Practice Regulations. Methods Thirty guinea-pigs were allocated to two groups: a control group 1 (five males and five females) and a treated group 2 (ten males and ten females). On day 1, in the dorsal region between the shoulders, intradermal injections of Freund's complete adjuvant mixed with the test substance (treated group) or the vehicle (control group) were prepared. On day 8, this same test site was treated by topical application of the test substance (treated group) or the vehicle (control group) and was covered by an occlusive dressing for 48 hours. After a rest period of 12 days, all animals of the treated and control groups were challenged by a topical application of the test substance to the right flank. The left flank served as control and received the vehicle only. Test substance and vehicle were maintained under an occlusive dressing for 24 hours. Skin reactions were evaluated approximately 24 and 48 hours later. Test substance concentrations were as follows:

Induction (treated group)

intradermal injections: DILAUROYL PEROXIDE at I% (w/w) in paraffin oil.

topical application: DILAUROYL PEROXIDE at 20% (w/w) in paraffin oil.

Challenge Call groups) .

topical application: DILAUROYL PEROXIDE at 1% (w/w) in paraffin oil.

At the end of the study, animals were killed. No skin samples were taken from the challenge application sites.

The sensitivity of the guinea-pigs in C.LT. experimental conditions were checked in a recent study with a positive sensitizer: 2,4-dinitro chlorobenzene. During induction period, the test substance was applied at 0.1% (day 1) and 1% (day 8) concentrations. At cutaneous challenge application, 1% (w/w) was tested on the right flank

No clinical signs and no deaths were noted during the study. No cutaneous reactions were observed after the challenge application. The guinea-pigs which were used in a recent study, showed a satisfactory sensitization response in 100% animals using a positive sensitizer.

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

Justification for classification or non-classification

The guinea pig maximization study demonstrates that dilauroyl peroxide does not meet the criteria for classification.