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EC number: 204-677-5
CAS number: 124-07-2
Skin irritation (OECD 404): corrosive Eye irritation (OECD 405), 70%: irritating
b: exposed skin brownish
n: skin necrotic
e: eschar formation
Table 2: Clinical signs of toxicity
Time after application
1 – 72 h
no specific findings
4 – 6 days
7 – 9 days
48 h – 6 days
1 h – 24 h
4 – 5 days
6 and 8 days
9 – 11 days
Table 3: Absolute body weight (kg)
start of study
72 h post application
end of observation period
Skin irritation after application of octanoic acid was
investigated in a GLP-study performed according to OECD guideline 404.
0.5 mL of 100% octanoic acid was applied to the clipped skin of three
New Zealand White rabbits under semi-occlusive conditions for 4 hours
(1984). The resulting mean scores over 24, 48 and 72 hours after
application were 3.0 and 1.8 for erythema and edema, respectively. The
also observed light-brown staining of the skin proved to indicate skin
necrosis, since a crust had formed 48 h after exposure. In each of the
animals the hairs failed to grow on day 7 after treatment, showing that
the dermis was affected in the deep. After the formation and loosening
of the crust, the skin had almost returned to normal 14 days after
exposure in the two animals, while the third animal showed a rather
scurfy skin and only partial restoration of hair growth. Based on the
findings, octanoic acid has to be considered as corrosive.
To determine the level of primary skin irritation of octanoic acid
under occluded conditions, 0.8 mL of octanoic acid at concentrations of
30%, 50%, 60%, 70% in PEG200/H2O and 100% was applied to the clipped
skin of 6 New Zealand White rabbits under occlusive conditions for 3
hours (1981a). While the mean scores for 24 and 48 hour readings were
both 0 for erythema and edema after application of 30%, 50%, 60%, 70%
octanoic acid, respectively, the scores were 3.3 for erythema and 3.2
for edema for 100% octanoic acid, respectively.
In another closed patch test by the same author, octanoic acid at
concentrations of 4%, 7.5%, 10%, 15% and 100% was tested by applying 0.4
mL to the clipped skin of 6 white rabbits under occlusion for 3 hours
(1981b). The resulting mean scores for erythema and edema were all 0 for
the dilutions of octanoic acid. At 100%, the resulting mean scores were
3.3 and 2.5 for erythema and edema, respectively.
The irritation after repeated administration was investigated in a
study, where five New Zealand White rabbits received applications of 0.8
mL octanoic at concentration of 55%, 60% 65% and 80% to the clipped skin
under occlusion for 3 hours/day on 7 consecutive days (1981c). Based on
the scores for erythema and edema the primary irritation index was
calculated with the combined scores for 30 min and 21-hour
post-treatment readings. The scores were 0.03, 0.03, 0.7, and >0.3 for
55%, 60%, 65% and 80% octanoic acid, respectively.
Possible corrosive properties were evaluated in a GLP - in vitro
test, where discs of freshly prepared rat skin were exposed to 150 µL of
octanoic acid for 24 hours followed by a measurement of the
transcutaneous electrical resistance (TER) (1994). Based on the
significant reduction in the measured mean resistance of the skin, the
authors concluded that octanoic acid displays properties characteristic
of those substances which may be corrosive to animal skin in vivo.
Whittle et al. published results of two in vitro tests on rat and
human skin (1996). The experiments with rat skin were performed similar
to OECD guideline 430. 150 µL of octanoic acid was added to the
epidermis of each freshly prepared rat skin disc for 24 hours. After
washing, the resistance measurements were conducted and resulted in a
TER of 2.5 kΩ. Since the TER decreased below 5 kΩ, octanoic acid is
considered to be corrosive to rat skin.
In the experiments with human skin, human skin samples (waste
material obtained from mammary cosmetic surgery, 9 donors) were also
exposed to 150 µL of octanoic acid for 24 hours. Tissue treated with
distilled water served as concurrent control. For none of the nine
donors the TER was decreased below the threshold value of 11 kΩ.
According to these results, octanoic acid is considered to be
non-corrosive to human skin.
In summary the available data indicate that octanoic acid has to
be regarded as corrosive to skin, while concentrations <=70% did not
lead to any skin irritation.
In a published study performed according to national guidelines,
octanoic acid was instilled into the eyes of six rabbits and considered
as eye irritant. Corneal opacity and moderate conjunctivitis did not
subside in 72 h (Briggs et al., 1976). Due to the limited information,
this study does not provide sufficient data for hazard assessment.
The eye irritation potential by octanoic acid at a concentration
of 70% was examined in a GLP study according to OECD guideline 405. 0.1
mL of 70% octanoic acid in vaseline was instilled into one eye each of 3
female New Zealand White rabbits (2011). The untreated left eye of each
animal served as control. After 24 h the eyes were rinsed. The eye
reactions were examined 24, 48 and 72 h after application and every 24 h
thereafter for up to 11 days. Under the conditions of the test, a single
ocular application produced irritant effects in the rabbits, which were
fully reversible within 6-11 days. The mean scores for corneal opacity,
iris, conjunctival redness and chemosis were 0.78, 0.66, 1.6 and 1
respectively. Since, in 2 out of 3 tested animals lesions of the iris
with a score equal to 1 were induced, octanoic acid has to be considered
as eye irritant at a concentration of 70%.
Based on the fact, that corrosion of the skin was found, octanoic
acid has to be regarded as serious eye damaging according to the
Guidance on CLP criteria, although the available studies rather indicate
an eye irritation potential.
The available data on skin
irritation/corrosion of octanoic acid meet the criteria for
classfication as Skin Corr. 1C, H314 according to Regulation (EC)
Data (1981a) revealed, that at and
below a concentration of 70% no irrating properties are present.
However, RAC does not support a specific concentration limit of 70% for
skin corrosion, as the available data do not allow for their
determination (RAC Opinion for
octanoic acid, June 2013).
on the fact, that corrosion of the skin was found, octanoic acid has to
be regarded as serious eye damaging according to the Guidance on CLP
classification for octanoic acid (7th ATP; Index: 607-708-00-4): Skin
Corr. 1C, H314
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