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EC number: 695-097-5
CAS number: 15789-90-9
Irritation:- Skin: irritating (rabbit)- eye: irritating (rabbit)
Under the conditions of this study, the test substance caused moderate
irritation to rabbit skin.
At 4 hours, produced marginal to distinct erythema and edema in
at 24 hours, the intensity of erythema and edema increased with
5/8 animals also showing marginal cracking;
at 48 hours, the intensity of erythema and edema stabilized and
6/8 animals had marginal to slight cracking with 1/8 animals having
marginal scaling and
at 72 hours, 1/8 rabbits showed no erythema or edema; 7/8 had
marginal to distinct erythema and edema; 7/8 had marginal to slight
cracking and 5/8 had marginal scaling.
The overall irritation score was 177, mean score per site was 22.13, and
mean score per site per day was 5.53.
12.5 %: irritant effects
- intense conjunctival irritation from days 1 to 4 involving chemosis
and discharge that cleared by day 7
- no corneal opacity or iris congestion
Irritant effects to skin were evaluated in a study, where eight
individually housed New Zealand White rabbits were
topically treated on the clipped dorsum (3-4 days prior to treatment)
with 0.5 ml undiluted test substance or standard under a semi-occlusive
patch (Quest, 1979). After removal of the patches, the sites were
assessed at 4, 24, 48, and 72 hours and graded for erythema, edema,
cracking and scaling on a scale ranging from “a” (marginal/very slight)
to “h” (severe). The observed effect included marginal to distinct
erythema and edema in most rabbits and marginal to slight cracking in
seven of eight animals and marginal scaling in five of eight animals
after 72 h. Although grades were converted to numerical scores and were
used for calculating, only the overall irritation score of 177 was
given. The mean score per site was 22.13 and the mean score per site per
day was 5.53. However, due to described irritation effects, methylionone
could be regarded as irritant to rabbit skin.
As part of a phototoxicity study a preliminary irritation test was
performed (Quest, 1982). A total of six males and nine females in groups
of five animals were treated with 0.1 ml of 10%, 30% or 100% of
methylionone in ethanol, respectively. The solution was applied to
clipped skin for 24 h. Skin reactions were assessed for erythema, edema,
cracking, scaling, dryness, hemorrhage, ulceration, scabbing and
exudation at 3, 6, 24, 48, and 72 hours using a standard 9-point scoring
system ranging from “0” (absent) to “9” (missing value). The
concentration causing minimal irritation was used for the
photoirritation test. Rats were weighed at the beginning and end of the
study. Application of 100% resulted in very slight to slight redness and
swelling at 3 and 6 hours with intensity increasing to slight at 24
hours and slight to distinct by 72 hours. Although no cracking and
scaling was observed until 24 hours, it was very slight and increased to
slight to distinct at 48 hours, and was distinct to well developed by 72
hours. Concentration of 30% and 10% showed weaker effects, so that the
author chose a concentration of 30% to be used for the main
phototoxicity study. Due to the described effect, methylionone could be
regarded as irritant to rat skin.
In another study, reading of irritant effects was only performed once
after application, so that the found redness in 6/8 animals after the
treatment under occlusion for 24 h was not further evaluated (Moreno,
Due to the lack of reliable studies regarding irritation to eyes of
methylionone, a study with iso-methyl-alpha-ionone (CAS 127 -51 -5), the
main constituent of the methyl ionone and structural analogue to all
methyl ionone isomers was taken into account. For more information on
the basis of the read-across please refer to the read-across
justification. In this study, 0.1 ml of a concentration of 12.5 % was
instilled into the right eye of 3 albino rabbits with no further
treatment while the untreated left eye served as a control. Both eyes
were examined every 24 hours for 4 days and on day 7 and scoring was
done according to the Draize scale for ocular lesions. No corneal
opacity or iris congestion was observed, but intense conjunctival
irritation from days 1 to 4 involving chemosis and discharge that
cleared by day 7 was noted. Since "intense conjunctival irritation" was
stated in reviews by Lapczynski et al. and Belsito et al. it could be
assumed that the resulting Draize score was >=2, thus reflecting the
irritant effects to eyes. Due to the structural similarity the same
result could be expected for methylionone.
Effects on skin irritation/corrosion: irritating
Effects on eye irritation: irritating
Due to positive results regarding skin and eye irritancy provided by
several studies using rabbits and rats, a classification is deemed
necessary for both eye and skin irritancy.
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