Is Cysteamine Really Gentler Than Thioglycolate? What the Science Says

In the lash and brow industry, cysteamine-based lifting solutions are often marketed as a “gentler” alternative to thioglycolate. But does the science support this claim? The short answer: not really.

While cysteamine is a newer reducing agent with some interesting properties, it has not been shown in published research to be gentler, safer, or more effective than thioglycolate. In fact, it performs differently — and not necessarily better.

What Are the Differences?

Both cysteamine and thioglycolate work by breaking disulfide bonds in keratin so the hair can be reshaped and “locked” into a new configuration during neutralization (Manuszak, 1993; Ghanem et al., 2025).

However, the kinetics and effectiveness differ:

• Thioglycolate acts faster, reducing more disulfide bonds in the same time frame.

• Cysteamine reacts more slowly and less completely under identical conditions.

• Thioglycolate follows predictable pseudo-first-order kinetics; cysteamine can exhibit moving-boundary kinetics at lower pH, making it harder to control.

Simply put, cysteamine breaks fewer bonds and may leave more hair unprocessed. That’s not necessarily “gentler” — it can also mean inconsistent results.

Why Do Brands Call It Gentler?

The perception that cysteamine is gentler seems to stem more from marketing than evidence. Because it acts slower and to a lesser degree, it might cause less visible damage if misused — but that hasn’t been demonstrated in controlled studies.

Thioglycolate, on the other hand, has decades of research and proven safety when used properly (Manuszak, 1993, p. 79). This is why it remains the gold standard in professional hair, lash, and brow services.

Regulatory Perspective: Banned in Japan

It’s also worth noting that cysteamine is currently banned for use in cosmetics in Japan. While not uncommon for regulatory bodies to differ, this underscores that cysteamine’s safety and efficacy are not universally accepted.

In contrast, thioglycolate continues to be approved and widely used worldwide — a testament to its long-standing track record.

Why Professionals Still Trust Thioglycolate

The bottom line: while cysteamine is a promising alternative worth studying further, current evidence does not support the claim that it is gentler or safer than thioglycolate.

When applied by a trained professional and neutralized correctly, thioglycolate remains the most predictable, effective, and reliable option.

References

Ghanem, H., et al. (2025). Effects of thioglycolate compounds in an emerging technique in the world of cosmetics—brow lamination.

Manuszak, M. A. (1993). A study of the effects of reduction by cysteamine and ammonium thioglycolate on the physical and chemical properties of hair (Master’s thesis, University of Cincinnati). University Microfilms International.