Potassium Persulfate

What it is

Potassium persulphate is what gives bleaching powder its power. Hydrogen peroxide alone lightens only to a limited degree; it is the persulphates in the powder that drive the process far enough for several levels in one working step. Without them there would be no bleaching powder in its present form.

This record differs from every other one in the lexicon in one respect: the best-documented finding concerns not the client but the person mixing the powder. In the occupational medicine literature persulphates are regarded as the main cause of work-related nasal and airway complaints in hairdressing — and the decisive route is not the skin but the air breathed in while mixing.

Why

• Why the classification reads “increased attention”: a systematic review published in 2022 evaluated 42 studies from two decades. Its finding: persulphates are regarded as the main cause of work-related rhinitis and asthma in hairdressers and, in some European countries, as one of the leading causes of occupational asthma altogether.
• The magnitude is considerable. One of the long-term studies evaluated found, among those aged 40 and over, an almost fourfold increased risk of wheezing and breathlessness compared with a control group, and an approximately twentyfold increased risk of developing respiratory symptoms in connection with bleaching powder at all.
• The decisive route is inhalation, not skin contact. Mixing the powder creates dust. That is exactly what the usual measures address: a separate mixing area, ventilation or extraction, low-dust preparations. For the client the process is short and does not take place over the bowl.
• Low-dust powder is no free pass. A Swedish study of people with bleaching-associated rhinitis found that switching to low-dust powder does not reliably prevent the symptoms. The expectation that lower-dust, cream or ready-to-use preparations reduce exposure is described by the review as plausible but not yet confirmed in actual exposure studies.
• The substance is no longer present in the result. Persulphates are consumed during lightening; what stays in the hair is the change to the fibre, not the substance. That is the same idea as with hydrogen peroxide and the reason why attention is directed at the application phase and not at the result.

When the assessment differs

• Salon staff: they are the group the findings relate to. Whoever mixes daily carries the highest exposure in the room.
• Apprentices and those new to the trade: the literature considers them separately because exposure begins early and symptoms often appear only after years.
• Existing asthma, allergic rhinitis or hay fever: pre-existing airway sensitivity lowers the threshold.
• Clients: short, infrequent exposure, no mixing. The classification applies here too, but its emphasis does not lie on this side.
• Irritated or broken scalp skin: the mixed product is alkaline and oxidising; on pre-damaged skin that carries more weight.

Open questions

• Concentration in the specific powder and in the mixed preparation: not available.
• Frequency of skin reactions to potassium persulphate as distinct from the related ammonium persulphate: not evaluated here. The figures used concern the airways.
• Effectiveness of individual protective measures in the salon: the review expressly states that the expected relief from low-dust or cream preparations has not yet been confirmed in actual exposure studies.
• Exposure of the client at a single appointment: not quantified. The studies evaluated look at long-term occupational exposure.
• Regulatory status: not checked; statements on use, maximum levels and workplace limits are not quoted second-hand.

Sources for this assessment

• Respiratory toxicity of persulphate salts and their adverse effects on airways in hairdressers — a systematic review. International Archives of Occupational and Environmental Health, 2022. Begutachtete systematische Übersichtsarbeit nach PRISMA, 42 ausgewertete Arbeiten, abgerufen am 10.09.2026.
• Nielsen J. u. a.: Dust-free bleaching powder may not prevent symptoms in hairdressers with bleaching-associated rhinitis. Journal of Occupational Health, Band 58, Heft 5, 2016, Seiten 470–476. Begutachtete Fachzeitschrift, abgerufen am 10.09.2026.

Related substances

Applies to: Oxidising agents

• Hydrogen Peroxide — Oxidising active ingredient

Further substances from the same group for which a long-form assessment already exists.