The active ingredient used in the first “cold wave” (cold permanent wave for hair) was thioglycolic acid.

What “cold wave” means

In this context, “cold wave” refers to a hair‑waving (permanent wave/perm) process that works without the high external heat used in early perms.

Instead, it relies on a chemical reducing agent to break and reform the hair’s disulfide bonds at or near room temperature.

Why thioglycolic acid?

  • Early cold‑wave formulations used thioglycolic acid as the key reducing agent to break hair’s disulfide bonds effectively at low temperatures.
  • Later systems evolved to use ammonium thioglycolate and then glyceryl monothioglycolate for gentler, “acid-balanced” or modern cold waves, but these came after the first thioglycolic‑acid–based cold waves.

Related ingredients in later cold waves

  • Ammonium thioglycolate became the main active ingredient in many standard cold-waving lotions (for example, early home waves like Toni).
  • Glyceryl monothioglycolate was introduced later for milder, acid-balanced cold waves popular from the 1970s onward.

TL;DR: In hairdressing history, the first true “cold wave” process used thioglycolic acid as its active ingredient.

Information gathered from public forums or data available on the internet and portrayed here.