Researchers from several Brazilian institutions have published a new study examining eight innovative hair straightening formulations aimed at providing safer, more effective options for different hair types and conditions.
The study, titled “Comparative Assessments of New Hair-Straightening Cosmetic Formulations on Wavy Type 2 Hair,” appears in the scientific journal Cosmetics and was conducted by scientists from the University of São Paulo, UNESP, and the Advanced Research Center in Medicine (CEPAM) at UNILAGO.
The study evaluated formulations containing active ingredients such as ammonium thioglycolate, amino methyl propanol (AMP) thioglycolate, and sodium cysteamine, comparing their performance on virgin, bleached, and chemically processed hair. The researchers sought to address key industry challenges, including the need for straightening products that modify hair texture without compromising its integrity.
Addressing a growing consumer trend toward natural hair
The study highlighted a key challenge in the cosmetics industry: the increasing demand for hair straightening products that work effectively on highly resistant hair textures without causing damage.
“The past decade has seen a consumer movement to return to natural hair,” the researchers noted. This shift has presented new challenges for salon professionals and product formulators, particularly as more individuals with Type 3 (curly) and Type 4 (tight curly) hair seek texture modifications.
To meet this demand, the researchers developed eight formulations using different combinations and concentrations of active ingredients, each tailored to specific hair types.
“Hair straighteners are among the most technically complex products to be safely and effectively developed,” the study stated. The researchers aimed to create new formulations that provide targeted performance while maintaining hair health by carefully controlling pH ranges, polymeric associations, and active ingredient concentrations.
The study compared eight formulations, each with specific active ingredients and intended hair types:
- Ammonium Thioglycolate (G03 and G04): These formulations, containing 13.3% and 9.4% ammonium thioglycolate, respectively, were found to be effective on wavy (Type 2) hair. Ammonium thioglycolate has been used as a straightening agent since the 1930s, and recent advancements in polymeric associations have enhanced its performance while reducing damage.
- Amino Methyl Propanol (AMP) Thioglycolate (G05 and G06): AMP thioglycolate, patented as BR 10 2013 017,342 8–INPI, was tested in concentrations of 12.5% and 7.9%. These formulations are recommended for finer or chemically processed hair due to their gentler action, which minimizes cuticle dilation and reduces damage.
- Sodium Cysteamine (G07 and G08): Sodium cysteamine formulations containing 5% and 4% active ingredient concentrations were found to be most effective for curly and tight curly hair (Types 3 and 4). The researchers observed improvements in hair fiber diameter, tensile strength, and luster. These formulations also showed reduced reliance on heat tools during application.
- Combination of Ammonium Thioglycolate and Sodium Thioglycolate (G09 and G10): The study explored formulations combining 2% and 1% of ammonium thioglycolate with sodium thioglycolate. This combination enhanced product penetration into more resistant hair fibers, making it suitable for wavy or curly hair with medium-to-coarse textures.
Key findings: Safety and effectiveness of new formulations
The researchers used various methods to assess the safety and effectiveness of the formulations, including mechanical and thermal resistance testing, fluorescence microscopy, scanning electron microscopy (SEM), and hair shine measurements.
One of the study’s significant findings was that all eight formulations achieved effective hair straightening while maintaining safety. “All formulations have been assessed and proved to be safe and effective for hair straightening, with different behaviors concerning some assessed parameters,” the researchers wrote.
Hair samples treated with ammonium thioglycolate demonstrated better alignment and shine than virgin hair. Meanwhile, sodium cysteamine formulations produced significant texture modifications in curly and tight curly hair types without excessive reliance on heat tools.
Thermal analysis results showed that sodium cysteamine formulations altered the structure of intermediate hair fibers at higher temperatures, contributing to their effectiveness on highly resistant hair.
The study also assessed hair porosity and cuticle damage using SEM imaging. The researchers found that higher concentrations of active ingredients led to increased hair permeation and structural changes.
Bleached hair samples showed the most significant cuticle damage, corroborating previous research that bleaching causes significant structural weakening. However, the researchers observed that formulations with lower active ingredient concentrations—such as AMP thioglycolate—offered a protective effect by limiting cuticle dilation.
Fluorescence microscopy revealed that straighteners with higher pH values, such as sodium cysteamine, achieved deeper penetration into hair fibers, resulting in more pronounced structural changes.
Conclusions and industry impact
The study concluded that polymeric associations—used to control the release of active ingredients—played a decisive role in achieving effective hair straightening while minimizing damage.
“Developing safe and effective hair straighteners is a significant challenge for the cosmetic industry,” the researchers stated. “These products must modify hair texture with minimal damage.”
Ultimately, the study provides a roadmap for creating next-generation hair straighteners that deliver targeted results for diverse hair types.
The research received no external funding, though Grandha Professional Hair Care donated materials. Additional support for testing was provided by the University of São Paulo’s DEINFAR Laboratory and the IPclin Group—Integrated Clinical Research Institute Ltd.
Source: Cosmetics
2024, 11, 222. https://doi.org/10.3390/cosmetics11060222
“Comparative Assessments of New Hair-Straightening Cosmetic Formulations on Wavy Type 2 Hair.”
Authors: Junior, C.M., et al.
