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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Toxicological information

Sensitisation data (human)

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Administrative data

sensitisation data (humans)
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Public available literature without indication of guideline and GLP

Data source

Reference Type:

Materials and methods

Type of sensitisation studied:
Study type:
study with volunteers
Test guideline
no guideline followed
GLP compliance:
not specified

Test material

Constituent 1
Chemical structure
Reference substance name:
Sodium hypochlorite
EC Number:
EC Name:
Sodium hypochlorite
Cas Number:
Molecular formula:
sodium hypochlorite
Details on test material:
Sodium hypochlorite
Sodium hypochlorite test mixtures:
- 1 wt% NaOCl
- 0.02 wt% Na2CO3
- different amounts of NaOH: 0.01, 0.03, 0.10, 0.30 or 1.00 wt%
- different volumes: 20 or 100 µL


Type of population:
Ethical approval:
not applicable
Sex: Not indicated
Age/weight: 20-61 years old (40.6 +/- 13.2) / not indicated
Known Diseases: free of any active skin disease
Number of persons: 50
Route of administration:
Details on study design:
Reason of exposure
Scientific research

Frequency of exposure

Overall time period of exposure
24 h

Duration of single exposure
24 h

Skin readings: The test sites were graded to a 5-point scoring scale (0 = no reaction, 0.5 = equivocal reaction, 1 = erythema, 2 = erythema and induration, 3 = erythema, induration and vesicles, 4 = erythema, induration and bullae) directly after test material removal and 24 h thereafter.
Skin colour reflectance was measured with a tri-stimulus reflectance meter using parameter a* (red hue).
Skin pH was measured before application, directly after removal of the patch and 24 h thereafter.
pH of test solutions: The pH of the test solutions were measured initially. The terminal pH were measured in the application chamber at the end of exposure.

Results and discussion

Results of examinations:
20 µL:
No induction of visible erythema nor significant changes in skin colour reflectance could be observed.
Measurements of skin pH showed an increased alkalinity directly after removal of the patch but returned to pre-treatment value measured after 24 h.
The mean pH of the residual test solutions after removal of the patch decreased from the initial values of 11.17-13-06 to 6.43-9.16.
100 µL:
Significant irritation was induced with highest scores for the 3 solutions of lowest NaOH concentration directly after removal of the patch. After 24 h irritation was higher with the highest score for the solution containing 0.10 % NaOH.
Measurements of skin pH showed results comparable to 20 µL application.
The mean pH of the residual test solutions after patch removal was consistently less decreased relative to initial values in comparison to the 20 µL application.

Applicant's summary and conclusion

The authors of this publication concluded that the study shows that irritancy of alkaline aqueous chlorine is a cumulative effect resulting from the three major oxidants/irritants present there in equilibrium: hypochlorite ion, hydroxide ion and hypochlorous acid.
They suggest that a non-irritant concentration for diagnostic patch testing for allergic contact dermatitis using 20 µL test volume could be as high as 1 % NaOCl and 1 % NaOH.
Executive summary:

In this study skin irritation induced by 24 h Patch testing with 20 µL or 100 µL containing constant NaOCl concentration (1 %) and different NaOH concentrations (0.01-1.00 %) was studied in adult human volunteers, by means of visual scores and skin colour reflectance measurements.

No irritation was observed by application of 20 µL 1 % OCl- independent of the NaOH concentration. However all solution induced significant irritation applying 100 µL. Skin reactions did not show a straight pH dose response as a maximum was seen at 0.1 % NaOH. Skin surface pH increased measured after removal of the patch but returned to initial values 24 h thereafter showing an efficient buffering capacity of human skin.