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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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

Administrative data

Description of key information

A skin sensitization study does not need to be conducted as the criteria are met for classification as corrosive to the skin. Effects on skin sensitization: not sensitizing.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records
skin sensitisation: in vitro
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance is classified as skin corrosion (Category 1, 1A, 1B or 1C)
Endpoint conclusion
Endpoint conclusion:
no study available

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Read-across Hypothesis

The reaction mass is composed of the following substances: sodium sulfite, sodium thiosulfate, sodium polysulfide and disodium sulfide, with residual amounts of sodium sulfate (see detailed description in section 1.2).

The read-across hypothesis is that the reaction mass can be considered as a mixture of the different salts and all the members of the reaction mass are various salts with sodium as cation and S-compounds as anion.

The main assumption is that the cationic species do not contribute significantly to any differences in solubility or toxicity and thus will not influence the toxicological endpoints under consideration. In dilute aqueous conditions the salts will be fully dissociated. Hence the properties as expressed in aqueous media for the mixture of the given salts can be directly read across with suitable mass correction to the individual components of the mixture which are as well dissociated.

As some toxicological data and classification of the individual constituents as well as the quantitative composition are known, data are evaluated in a weight-of-evidence approach for the mixture of those constituents.


Conclusions per endpoint for C&L: Skin sensitization

The reaction mass is classified as skin corrosive based on properties of the constituents disodium polysulfide and sodium sulfide. Moreover, due to the alkaline nature of those constituents, any animal testing for assessment of the sensitization potential is not scientifically justifiable. It would, moreover, not provide any relevant information for the risk assessment of workers or the general population. Therefore, following the specific rules for adaption in line with section 8.3, column 2, Annex VII, of Regulation (EC) 1907/2006, a skin sensitization study does not need to be conducted as the criteria are met for classification as corrosive to the skin.

Beyond this aspect, the available public information on the constituents of the reaction mass do not show any alert of skin sensitization. Sulfides also occur endogenously under physiological conditions. Sulfites can occur naturally in foods as a consequence of fermentation, but they are also added to foods as preservatives. 

The REACH dossier on sodium sulfite (CAS 7757-83-7, see: summarizes that reported human incidences of sulfite sensitivity have been reviewed extensively by various scientific and regulatory bodies in the EU, concluding on an absence of skin sensitizing effects.

Among those reviews is the conclusion of the MAK commission of 2014 on sulfites (, accessed on 03.02.2021). Sodium metabisulfite, potassium metabisulfite and sodium bisulfite are not designated as dermal sensitizers in view of the very small number of persons epidermally sensitized despite their widespread use and numerous possibilities for contact in everyday life.

In the OECD SIDS assessment for disodium disulfite of 2001 (, accessed on 03.02.2021), some reports in humans related to urticaria and asthma with itching, edema, rhinitis, and nasal congestion are cited. However, an immunological pathogenesis of these reactions was not clear. In a non-guideline study, no indication of skin sensitization for guinea pig was observed, but in a few cases, allergic contact dermatitis as well as positive patch-testing was reported in humans. Overall, with respect to its widespread use, the OECD SIDS concluded that disodium disulfite is not considered a skin sensitizer and is also unlikely to induce respiratory sensitization but may enhance symptoms of asthma in sensitive individuals.

The reviews of the Scientific Committee on Cosmetic Products and Non-Food Products Intended for Consumers (SCCNFP, 2003,, accessed on 03.02.2021) and the Cosmetic Ingredient Review Expert Panel (CIR, 2003, Int J Toxicol. 2003; 22 Suppl 2:63-88) are in lines with those conclusions.

Available information on constituents of the reaction mass do not indicate a concern for skin sensitization, therefore, a classification for this endpoint is not warranted. The classification criteria according to Regulation (EC) 1272/2008 as skin sensitizer are not met.