Safety and health

We explain how historical techniques worked because that is part of their history. We do not give instructions for chemical processes, and we never reproduce historical recipes containing lead, mercury or unknown ingredients for anyone to use.

Explanations of hair chemistry — bonds, pH, heat — are written in general terms and will be reviewed by experts. Pages that mention risk will be reviewed for safety. Each technique’s record says whether that review has happened yet and, once it has, gives its date.

Current guidance

We link only to authoritative, current guidance, and we check these links at least once a year.

Safety note

This site is historical and educational. It is not medical, chemical or hairdressing advice. For current guidance:

The British Association of Dermatologists explains that repeated tension from tight ponytails, buns, braids, locs, extensions or weaves may cause traction alopecia. (The leaflet is past its own review date; we will replace it when a revised version appears.) Traction alopecia (British Association of Dermatologists; link checked 25 September 2026)
The NHS warns that PPD, found in many permanent and some semi-permanent dyes, can cause irritation or allergy. Hair dye reactions (NHS; link checked 25 September 2026)
The US Food and Drug Administration warns that some smoothing products release formaldehyde gas when heated. Hair Smoothing Products That Release Formaldehyde When Heated (US Food and Drug Administration; link checked 12 November 2026)
The British Association of Dermatologists publishes patient information on caring for Afro-textured hair. Caring for Afro-textured hair (British Association of Dermatologists; link checked 25 September 2026)

Images and wellbeing

We avoid before-and-after framing that treats natural texture, grey hair or hair loss as a problem to be fixed. Pages discussing hair loss, illness or chemical injury carry a content note at the top.

Last updated 12 November 2026.