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Description of key information

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
skin sensitisation: in vivo (LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from 08 November 2012 to 20 November 2012
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well documented GLP study performed according to OECD Guideline 429 and EU Method B.42.
according to
OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)
according to
EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)
GLP compliance:
yes (incl. certificate)
Type of study:
mouse local lymph node assay (LLNA)
Details on test animals and environmental conditions:
- Source: Harlan Laboratories UK Ltd., Oxon, UK
- Age at study initiation: eight to twelve weeks old
- Weight at study initiation: 15 to 23 g
- Housing: The animals were housed in suspended solid-floor polypropylene cages furnished with softwood woodflakes
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: at least five days

- Temperature (°C): 19 to 25 °C
- Humidity (%): 30 to 70%
- Air changes (per hr): 15 changes per hour
- Photoperiod (hrs dark / hrs light): twelve hours continuous light (06.00 to 18.00) and twelve hours darkness

propylene glycol
2.5% v/v
Preliminary screening test:
25 µL of the test item at a concentration of 25% w/w in propylene glycol. This concentration was selected as maximum concentration suitable for dosing in solubility trials.

Main test:
Test item at concentrations of 25%, 10% or 5% w/w in propylene glycol. These concentrations were selected as, at 25%, no excessive irritation was noted.
No. of animals per dose:
four animals
Details on study design:
- Compound solubility: the solubility of the test item in different vehicles was determined on the basis of maximising the concentration and solubility whilst producing a solution/suspension suitable for application. The vehicles tested were: acetone/olive oil (4:1), dimethyl formamide, butanone, dimethyl sulphoxide, acetone, ethanol/distilled water (7:3), 1% pluronic L92 in distilled water and propylene glycol. The concentrations tested were 50% (0.5 g test item + 0.5 g vehicle) and 25 % (1 g of 50% dilution made up to 2 g).
- Irritation: A preliminary screening test was performed using one mouse. The mouse was treated by daily application of 25 µL of the test item at a concentration of 25% w/w in propylene glycol, to the dorsal surface of each ear for three consecutive days (day 1, 2, 3). The mouse was observed twice daily on days 1, 2, and 3 and once daily on days 4, 5 and 6. Local skin irritation was scored daily. No signs of systemic toxicity, visual local skin irritation or irritation indicated by an equal to or greater than 25% increase in mean ear thickness were noted. Based on this information the dose levels selected for the main test were 25%, 10% and 5% w/w in propylene glycol.
- Lymph node proliferation response: The thickness of each ear was measured using an Oditest micrometer, pre-dose on Day 1, post dose on day 3 and on day 6. Any changes in the ear thickness were noted. Mean ear thickness changes were calculated between time periods days 1 and 3 and days 1 and 6. A mean ear thickness increase of equal to or greater than 25% was considered to indicate excessive irritation and limited biological relevance to the endpoint of sensitisation.

- Name of test method: After the acclimatisation the animals were selected at random and given a number unique within the study by indelible ink-marking on the tail and a number written on a cage card.
- Criteria used to consider a positive response: The proliferation response of lymph node cells was expressed as the number of radioactive disintegrations per minute per lymph node (disintegrations per minute/node) and as the ratio of 3HTdR incorporation into lymph node cells of test nodes relative to that recorded for the control nodes (stimulation index). The test item is regarded as a sensitiser if at least one concentration of the test item results in a threefold or greater increase in 3HTdR incorporation compared to control values. Any test item failing to produce a threefold or greater increase in 3HTdR incorporation is classified as a "non-sensitiser".

TREATMENT PREPARATION AND ADMINISTRATION: For the purpose of the study, the test item was freshly prepared as a suspension in propylene glycol. This vehicle was chosen as it produced the highest concentration that was suitable for dosing. All vehicles tried at 50% were unsuitable for the LLNA test. The test item was formulated within two hours of being applied to the test system. It is assumed that the formulation was stable for this duration.
Positive control substance(s):
other: Phenylacetaldehyde
No data
Positive control results:
DPM: 70878.16
Stimulation index: 18.93
Result: positive
Remarks on result:
other: Test item stimulation index: 0.74 (5% w/w in propylene glycol) 1.90 (10% w/w in propylene glycol) 1.97 (25% w/w in propylene glycol)
other: disintegrations per minute (DPM)
Remarks on result:
other: 3744.41 (vehicle) 2768.51 (5% w/w in propylene glycol) 7127.13 (10% w/w in propylene glycol) 7364.06 (25% w/w in propylene glycol)


The vehicle suitable for dosing was propylene glycol.

Clinical signs and mortality data:

There were no deaths. No signs of systemic toxicity were noted in the test or control animals during the test.


Bodyweight changes of the test animals between day 1 and day 6 were comparable to those observed in the corresponding control group animals over the same period.

Ear thickness measurements and ear thickness changes, local skin irritation:

There was no increase in ear thickness (> 25%) in any of the test or control animals on days 3 and 6. No signs of irritation were seen in any of the animals throughout the test.

Interpretation of results:
not sensitising
Migrated information Criteria used for interpretation of results: EU
The test item was considered to be non-sensitiser under the conditions of the test according to CLP/GHS criteria.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

Following a preliminary screening test in which no clinical signs of toxicity were noted at a concentration of 25% w/w, this concentration was selected as the highest dose investigated in the main test of the local lymph node assay. Three groups, each of four animals, were treated with 50 µL (25 µL per ear) of the test item as a suspension in propylene glycol at concentrations of 25%, 10% or 5% w/w. A further group of four animals was treated with propylene glycol alone. A concurrent positive control test, using a group of four animals, was also performed with the known sensitiser, phenylacetaldehyde at a concentration of 2.5 % v/v in propylene glycol.

The stimulation index expressed as the mean radioactive incorporation for each treatment group divided by the mean radioactive incorporation of the vehicle control group as follows:

 Treatment group  Concentration  Stimulation index  Result
 Test item  5% w/w in propylene glycol  0.74  negative
 Test item  10% w/w in propylene glycol  1.90  negative
 Test item 25% w/w in propylene glycol   1.97  negative
 Positive control item  2.5% v/v in propylene glycol  18.93  positive

The test item was considered to be a non-sensitiser under the conditions of the test according to CLP criteria.

Phenylacetaldehyde gave a stimulation index of greater than 3 when tested at a concentration of 2.5% v/v in propylene glycol.

Migrated from Short description of key information:
In a local lymph node assay in the mouse according to OECD Guideline 429 and EU Method B.42, lanthanum acetate was observed not to be sensitising to the skin (Henzell, 2013).

Justification for selection of skin sensitisation endpoint:
There is only one study available.

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Based on the study results and the criteria of the DSD and CLP Regulation, lanthanum acetate should not be classified as skin sensitising substance.