Salicylic acid

Endpoint summary

Description of key information

Not sensitising to the skin

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

no data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The MEST test is accepted by OECD as a screening method in sensitization. The publication is well documented and scientifically acceptable for assessment. GLP compliance is not mentioned.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Method: Mouse ear swelling test. The test animals are initially injected twice with FCA (Freund’s complete Adjuvant) into the abdomen. Animals were then topically dosed with test material in solvent or solvent alone (for controls) applied to the center of the shaved region on the abdominal skin. Topical application of the appropriate solution to the abdomen was repeated for three additional consecutive days. Seven days after the final topical application to the abdomen, test compound in solution was applied to the left ear of each animal (test and control) and the solvent was applied to the right ear. At both 24 and 48 hr after this challenge, the thicknesses of both ears measured.

GLP compliance:

not specified

Type of study:

mouse ear swelling test

Justification for non-LLNA method:

alternative method, published in an article.

Species:

mouse

Strain:

CF-1

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories
- Age at study initiation: 6-8 weeks
- Weight at study initiation: no data
- Housing: five per cage
- Diet : ad libitum, Purina Rodent Laboratory Chow 5001
- Water :ad libitum
- Acclimation period: a week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): no data
- Humidity (%): no data
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): no data

IN-LIFE DATES: no data

Route:

epicutaneous, open

Vehicle:

other: acetone

Concentration / amount:

10 % (Basis for selection of concentration: solubility)

Route:

epicutaneous, open

Vehicle:

other: acetone

Concentration / amount:

10 % (Basis for selection of concentration: solubility)

No. of animals per dose:

Test group: 10-15 animals
Control group: 5-10 animals

Details on study design:

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 3
- Day(s) of exposure: 1;2;3
- Test groups: 100 µl of test substance in vehicle
- Control group: 100 µl of vehicle
- Site: abdominal skin
- Concentrations: 10 %

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: 10
- Test groups: 20 µl of test substance in vehicle and 20 µl of vehicle
- Control group: 20 µl of test substance in vehicle and 20 µl of vehicle
- Site: left and right ear
- Concentrations: 10 %
- Evaluation (hr after challenge): 24 and 48

Positive control substance(s):

no

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

10%

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: test group. Dose level: 10%. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: none.

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

10%

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: test group. Dose level: 10%. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: none.

Salicylic acid did not induce sensitization in mice in the mouse Ear Swelling Test (MEST).

% swelling = [(test ear thickness) / (control ear thickness)] x 100 = 102%
No mice were sensitized.

Interpretation of results:

GHS criteria not met

Conclusions:

Classification: not sensitizing

Executive summary:

In a development and validation study of alternative dermal sensitization (Gad et al, 1986), salicylic acid were tested using the method of Mouse Ear Swelling Test (MEST). The aim of this study was to develop and optimize a protocol for the MEST. To evaluate the performance of this final MEST study design, a battery of 72 test materials among them was salicylic acid (for which the sensitizing potential in the guinea pig maximization test (GMPT) and/or in humans was already known) was evaluated. CF-1 female mice, 6 to 8 weeks old were used. In this study, salicylic acid is not a dermal sensitizer.

Reference 2

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Slightly modified LLNA study with no information on GLP status

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

yes

Remarks:

Application of test substance on 4 days, with evaluation on Day 5

GLP compliance:

not specified

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

CBA

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Jackson Labs (Bar Harbor ME) or NCI (Fredrick, MD)
- Age at study initiation: 6-9 weeks
- Weight at study initiation: no data
- Housing: no data
- Diet (e.g. ad libitum): no data
- Water (e.g. ad libitum): no data
- Acclimation period: no data

ENVIRONMENTAL CONDITIONS
no data

IN-LIFE DATES: no data

Vehicle:

other: acetone

Concentration:

1, 10, 20%

No. of animals per dose:

5

Details on study design:

MAIN STUDY
ANIMAL ASSIGNMENT AND TREATMENT
- Name of test method: LLNA
- Criteria used to consider a positive response: SI >= 2 and statistically significant from vehicle-treated control (p>0.01)

Positive control substance(s):

other: 1-chloro-2,4,6-trinitrobenzene

Statistics:

Intergroup comparisons based on analysis of variance or distribution free methods. Bartlett's test of homogeneity of variance, and least significance difference or Wilcoxon's rank sum test.

Positive control results:

TNCB dpm-fold increase: 0.01%: 18.0; 0.05%: 80.3; 0.10%: 103.3

Parameter:

SI

Value:

0.9

Test group / Remarks:

1%

Parameter:

SI

Value:

1.8

Test group / Remarks:

10%

Parameter:

SI

Value:

7.2

Test group / Remarks:

20%

Parameter:

SI

Value:

1

Test group / Remarks:

acetone

Parameter:

other: disintegrations per minute (DPM)

Value:

350

Test group / Remarks:

1%

Parameter:

other: disintegrations per minute (DPM)

Value:

736

Test group / Remarks:

10%

Parameter:

other: disintegrations per minute (DPM)

Value:

2 950

Test group / Remarks:

20%

Parameter:

other: disintegrations per minute (DPM)

Value:

408

Test group / Remarks:

acetone

Interpretation of results:

Category 1 (skin sensitising) based on GHS criteria

Conclusions:

Under the conditions of the present assay, SA was shown to have weak to moderate sensitization potential.

Executive summary:

Salicylic acid was one of 17 chemicals tested in an examination of the LLNA assay for use in contact sensitization risk assessment (Gerberick, 1992).

In a slightly modified LLNA protocol, test items were applied on both surfaces of ears of 5 femaleCBA/J mice per group (25 µl/ear) for four consecutive days (Days 1, 2, 3 and 4). SA was tested at concentrations of 0, 1, 10 and 20% in acetone. On Day 5, the cell proliferation in the local lymph nodes was measured for each individual mouse by incorporation of tritiated methyl thymidine ([³H]TdR). The values obtained were used to calculate stimulation indices (SI).

A chemical was considered positive (sensitizer) in this assay if exposure to at least one concentration resulted in a 2-fold or greater increase in [³H]TdR, expressed as disintegrations per minute (dpm) provided that this mean dpn value was statistically different from vehicle-treated mice (p=< 0.01). Chemicals wee considered to be moderate to strong sensitizers if the increase was >30-fold and weak to moderate sensitiser if the increase was 2-30-fold over vehicle-treated mice.

Stimulation index values for SA were 7.2, 1.8 and 0.9 at treatment concentrations of 20, 10 and 1%, respectively.

Under the conditions of this assay, SA tested in acetone, was considered to be a weak to moderate sensitizer.

Reference 3

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Modification of LLNA protocol

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Deviations:

yes

Remarks:

Evaluation of proliferation by light microscopy

GLP compliance:

not specified

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

CD-1

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Charles river, France
- Age at study initiation: 6-8 weeks

Vehicle:

acetone/olive oil (4:1 v/v)

Concentration:

5, 10, 20%

No. of animals per dose:

4

Statistics:

one-way analysis of variance; pairwise comparison with control by Dunnett's procedure; homogeneity of variance by Levene's test; normality of residuals by normal probability plot & Shapiro-Wlik's test.

Parameter:

other: T/C ratio

Value:

1.74

Remarks on result:

other: See below

Statistically significant T-lymphocyte proliferation in the paracortex was detected in short, but not long, protocol. The maximum T/C ratio was 1.74. No proliferation was detected in the cortex.

Rare, very slight, paracortical hyperplasia was detected by both protocols.

These results were comparable to those obtained for another irritant, sodium lauryl sulphate, in the same study.

The authors considered the threshold for a positive result in this assay to be 1.75. Under these conditions, SA at 20% concentration is not sensitising.

Interpretation of results:

GHS criteria not met

Conclusions:

The weak proliferative effects obtained using the short protocol was below the threshold for a positive reaction in this assay. SA was considered not sensitising.

Executive summary:

In a variation on the mouse local lymph node assay, two protocols were used. In the short protocol, topical administration of 25 ul to both ears on Day 1, 2 & 3 was followed by bromodeoxyuridine (BrdU) intraperitoneal injection and euthanasia on Day 5. In the long protocol, topical application of 50 ul to flank on Day 1 was followed by patch removal on Day 3, topical application of 25 ul to both ears on Days 6, 7, 8, BrdU i.p. injection & euthanasia on Day 9. The draining auricular lymph nodes were excised, weighed and fixed. Two successive sections were taken through mid-sagittal plane. One section was stained with haematoxylin and eosin for microscopic examination. The following section was processed for immunohistochemistry and labelled nuclei counting.

Statistically significant T-lymphocyte proliferation in the paracortex was detected in short, but not long, protocol. The maximum T/C ratio was 1.74. No proliferation was detected in the cortex. Rare very slight, paracortical hyperplasia was detected by both protocols.

These results were comparable to those obtained for another irritant, sodium lauryl sulphate, in the same study.

The authors considered the threshold for a positive result in this assay to be 1.75. Under these conditions, SA at 20% concentration is not sensitising.

Reference 4

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

no data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study, but only limited experimental data are provided in the publication.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

GLP compliance:

not specified

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

CBA

Sex:

not specified

Vehicle:

not specified

Concentration:

5, 10, 25%

No. of animals per dose:

4

Parameter:

SI

Value:

0.8

Test group / Remarks:

5%

Parameter:

SI

Value:

1.5

Test group / Remarks:

10%

Parameter:

SI

Value:

2.5

Test group / Remarks:

25%

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: No data

Interpretation of results:

GHS criteria not met

Conclusions:

SA is not considered to show skin sensitising properties in this test system.

Executive summary:

In a study of the sensitizing potential of a number of chemicals with irritant properties (Basketter et al, 1998), groups of 4 mice received 25µL SA dissolved in a vehicle (not specified) at concentrations of 5, 10 and 25% on the dorsum of both ears daily for 3 consecutive days. All mice were injected intravenously 5 days after the first treatment, with 250µL PBS containing 20 uCi of [3H]thymidine. 5 hours later, the draining auricular lymph nodes were excised and pooled for each group and a single cell suspension of lymph node cells was prepared. thymidine incorporation was measured with beta-scintillation counting.

SA showed a non-significant dose-related increase in cell proliferation, and did not give a positive result (SI >3) at any tested concentration. No EC₃ value could be calculated. SA was not considered to be a skin sensitiser in this test.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

SA was tested as part of the evaluation of the Mouse Ear Swelling Test (MEST) (Gad et al, 1986) and was evaluated as being not sensitizing when tested at 10%, the maximum concentration soluble in the vehicle (acetone). SA was also tested in three studies evaluating the LLNA, at up to 25% concentration. These studies are summarized in Table 1. Only one of the studies (Gerberick, 1992) reported SI >3 at 20%, concluding SA to be a weak to moderate sensitizer, while another (Basketter, 1998) showed no evidence of sensitization at 25% concentration. Overall, it is concluded that SA does not have significant sensitization potential.

Table 1: LLNA Studies

Concentrations	Stimulation indices	Result	Reference	Klim.
5, 10, 25%	0.9, 1.5, 2.5	Negative	Basketter, 1998	2
1, 10, 20%	0.9, 1.8, 7.2	Positive	Gerberick, 1992	2
5, 10, 20%	Max T/C ratio 1.74	Negative	Boussiquet-Leroux, 1992	2

 

Migrated from Short description of key information:
The majority of the sensitization studies on SA showed non-sensitizing results. However, since one LLNA study gave a positive response, a weight of evidence approach has been used to assess this endpoint. Studies used are a mouse ear swelling test (Gad et al, 1986) and LLNA studies (Basketter, 1998; Gerberick, 1992; Boussiquet-Leroux, 1992). It is concluded that SA does not have significant sensitizing properties.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

No reports of human respiratory sensitization have been found over many years' experience of use. It is concluded that SA does not have potential to cause respiratory sensitization in humans. In a clinical study (Zhu, 1997), SA did not induce IgE on oral challenge.

 

Migrated from Short description of key information:
No reports of human respiratory sensitization have been found. It is concluded that SA does not have potential to cause respiratory sensitization in humans. In a clinical study (Zhu, 1997), SA did not induce IgE on oral challenge.

Justification for selection of respiratory sensitisation endpoint:
Based on weight of evidence

Justification for classification or non-classification

Skin sensitisation:

Not sensitising according to EU and GHS (UN/EU) criteria.

Based on weight of evidence from MEST test and LLNA studies.

Respiratory sensitisation:

Not sensitising according to EU and GHS (UN/EU) criteria.

Based on absence of report of human sensitisation over many years experience.