RESORCINOL

Name / description

Resorcinol, 1,3-Dihydroxybenzene, 3-Hydroxyphenol

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Function(s) of this ingredient in cosmetic products

HAIR DYEING

Colours the hair

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Origin

synthetic

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Occurrence in cosmetics

Oxidation hair colourant (permanent hair dyes)

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Occurrence in other products

Medical external applications (ointments / creams for external application) for acne treatment; paper, paints, rubber, textiles

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Background information on use in cosmetics

Cosmetic hair dyes are subdivided according to different operating principles. There are temporary dyes (tints), semi-permanent dyes (semi-permanent hair colours) and permanent dyes (oxidation dyes or bleaches). Temporary dyes are characterised by the use of direct dyes (eg cationic dyes such as Basic Red 56 or Acid Blue 62). There is no chemical reaction with other components; the dyes adhere to the hair surface and last for one to two hair washes. For temporary hair dyes, azo, triphenylmethane or anthraquinone dyes are used. The temporary dyes are sold as aqueous alcoholic solutions. In combination with hairspray, it is also possible to apply very small golden or silver gloss pigments or even fluorescent substances to the hair. Semi-permanent dyes (tints) also use direct dyes (eg nitro dyes such as HC Blue 2 or HC Yellow 10). The hair is coloured circularly, which ensures that it lasts for eight to 10 hair washes. Nitro dyes diffuse because of their low molecular size into the hair but are washable. Other dyes which are used include nitrophenyl diamines, azo and quinonimine dyes in combination with organic solubilizers such as glycol ether or polypropylene. In the event of permanent dyes (oxidative hair dyes), colourless precursors, also referred to as developers and couplers, are first used. The actual dyes are formed through a chemical reaction. The entire hair is dyed and the colour is not washable.

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Information on safe use

Hair colourants are at present amongst the most thoroughly examined cosmetic products on the EU market. Since 2003 the European Commission has pursued a global strategy for the safety assessment of hair colourants and hair dyes in Europe. More than 100 individual hair colourants were considered as safe by the Scientific Committee for Consumer Safety (SCCS) of the EU Commission after a comprehensive assessment and are allowed for use in Annex III of the EC Cosmetics Regulation. Publication of the EU Commission on the Safety of hair dyes This substance is expressly approved and / or subject to a restriction as a result of an entry in Annex III of the EC Cosmetics Regulation after an assessment by the Scientific Committee on Consumer Safety of the EU Commission (SCCS). Restrictions can relate eg to purity criteria, a maximum concentration or the restriction to certain product categories. Subject to the conditions possibly imposed in Annex III, the use of this substance in cosmetic products is safe.

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Links to scientific assessments

Opinion of the SCCS (2021) on the safety of resorcinol

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Why are we talking about it?

Resorcinol is suspected of being an endocrine disruptor, and of being irritating to the skin, eyes and respiratory tract. The facts: The use of resorcinol is restricted to certain categories of hair products, partly reserved to professionals. Concentrations of resorcinol in these products are low. This limited exposure allows for safety margins which are much higher than the required margin (400 times higher) (1). In vitro studies (i.e. carried out in an artificial environment: in the laboratory, for instance in a test tube) have shown an effect on the synthesis of thyroid hormones. In vivo results (i.e. studies carried out on living organisms) are contradictory but some studies show a reversible effect on thyroid hormones (2). Endocrine disruption is a recent concept, which explains why there are more in vitro data, which are quicker and easier to produce, than in vivo data. European scientific experts have once more assessed the safety of resorcinol at the concentrations used in cosmetics in 2020 by re-analysing all data, including on endocrine disruption, and concluded that it is safe for consumers (3). Resorcinol is a moderate skin sensitizer but the frequency of contact allergies in humans is low. Key points to take away: The use of resorcinol is limited to certain types of cosmetic products and to low concentrations. In these circumstances, its use in cosmetic products was once again evaluated in 2020 and considered safe for human health according to European and French experts. Sources: (1) Cosmetic Products Regulation (EC) No 1223/2009; Annex III (2) Resorcinol - ECHA - Dossier Annex XV - Proposal for identification of a substance of very high concern on the basis of the criteria set out in reach article 57 (2020): https://echa.europa.eu/documents/10162/c224d018-6c7d-b592-bad4-79bb779f173e (3) Scientific Committee on Consumer Safety: Opinion SCCS/1619/20: https://ec.europa.eu/health/sites/health/files/scientific_committees/consumer_safety/docs/sccs_o_241.pdf

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Further information

For the clarification of a suspicion of a contact allergy this substance can be routinely tested in the epicutaneous test at the dermatologist.

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Belongs to the following substance groups