What happens to hair’s protein structure with relaxers?

Roots

The journey of understanding our hair often begins with a quiet contemplation of its very nature. We observe its spirals, its waves, its gentle curves, and perhaps its resistance to certain manipulations. For many, especially those with textured hair, this observation deepens into a consideration of how to shape and care for these unique strands.

When we consider chemical relaxers, we step into a realm where the desire for altered form meets the profound chemistry of hair itself. To truly grasp what happens when a relaxer touches hair, we must first appreciate the intricate world hidden within each strand.

At its core, hair is a remarkably resilient protein fiber. This resilience comes from its primary building block, Keratin, a protein rich in an amino acid called cysteine. Cysteine residues are unique because they contain sulfur atoms, which readily form strong chemical connections known as Disulfide Bonds. These bonds are the architects of hair’s inherent shape, providing the structural integrity that gives curls their spring and coils their tight formation.

Imagine these disulfide bonds as tiny, robust bridges connecting long protein chains within the hair’s cortex, the innermost and most substantial layer of the hair shaft. The sheer number and arrangement of these bridges determine the hair’s natural curl pattern.

Beyond disulfide bonds, hair also possesses weaker, yet still influential, hydrogen bonds and salt bonds. These bonds are more transient, easily broken by water or heat, and then reformed as hair dries or cools. This is why a simple wash-and-go can temporarily alter curl definition, or why heat styling can straighten hair until the next wash.

However, the disulfide bonds are different; they are the permanent anchors, the very blueprint of the hair’s form. Any alteration to these bonds requires a powerful chemical intervention.

Hair’s natural curl is deeply rooted in the strong disulfide bonds within its keratin protein structure.

The Chemical Symphony of Relaxers

Chemical relaxers are powerful alkaline formulations designed to permanently alter the hair’s natural curl by targeting these robust disulfide bonds. The two most common types of relaxers are hydroxide-based (often called “lye” or “no-lye” relaxers) and thioglycolate-based (“thio”) relaxers. While their precise chemical pathways differ, their ultimate goal is the same ❉ to dismantle the disulfide bridges and allow the hair to be reshaped into a straighter configuration.

Hydroxide Relaxers, such as those containing sodium hydroxide, potassium hydroxide, lithium hydroxide, or guanidine hydroxide, operate at a very high pH, typically between 12 and 14. This extreme alkalinity causes the hair shaft to swell significantly, sometimes doubling its normal diameter, allowing the active ingredients to penetrate the protective cuticle layer and reach the cortex. Once inside, the hydroxide ions initiate a process called Lanthionization. This is not merely a bond-breaking action; it is a profound chemical conversion.

In lanthionization, one sulfur atom is removed from a disulfide bond, and the remaining sulfur atom then reacts to form a new, single sulfur bond called a lanthionine bond. This new bond is irreversible; it cannot be reformed back into a disulfide bond. This permanent alteration is why relaxed hair does not revert to its natural curl pattern, even when wet.

Thioglycolate Relaxers, often using ammonium thioglycolate, operate through a different mechanism, though still at an alkaline pH, usually above 10. These relaxers are reducing agents. They break the disulfide bonds by adding hydrogen atoms to each sulfur atom in the bond, converting the disulfide bond into two separate sulfhydryl groups (-SH). Unlike hydroxide relaxers, the broken bonds in thio-relaxed hair can, in theory, be reformed.

This is why thio relaxers require a “neutralizer,” typically hydrogen peroxide, in a second step. The neutralizer oxidizes the sulfhydryl groups, allowing new disulfide bonds to form in the hair’s newly straightened configuration.

Regardless of the chemical pathway, the fundamental change is a dramatic reorganization of the hair’s internal architecture. The strong, stabilizing disulfide bonds that dictated the hair’s natural curl are broken and either irreversibly replaced with lanthionine bonds or temporarily broken and then reformed in a new, straightened alignment. This chemical manipulation, while achieving the desired aesthetic, inevitably impacts the hair’s intrinsic strength and resilience.

Ritual

For generations, the application of relaxers has been more than a chemical process; it has been a deeply ingrained practice, a part of many hair care traditions, particularly within Black communities. This practice, often performed in salons or at home, represents a commitment to a particular aesthetic and a desire for hair manageability. Understanding the precise steps and the underlying alterations during this ritual reveals the delicate balance between desired outcome and potential consequences for the hair’s protein structure.

The ritual begins with preparing the hair and scalp. For lye relaxers, a protective base cream is often applied to the scalp to shield it from the highly caustic chemicals. Even “no-lye” relaxers, while perceived as milder, can still cause irritation and burns, necessitating similar precautions around the hairline and ears. This initial step underscores the potency of the chemicals involved, a quiet acknowledgment of the significant transformation about to unfold.

The Transformation on a Molecular Level

Once the relaxer cream is applied to the hair, it begins its work by causing the hair shaft to swell. This swelling facilitates the penetration of the active chemical agents into the hair’s cortex, where the keratin proteins reside. As the chemicals penetrate, they initiate the bond-breaking reactions.

• Disulfide Bond Breakage is the primary action. Hydroxide relaxers cleave these bonds and convert them into lanthionine bonds, a permanent structural change. Thio relaxers reduce the disulfide bonds into sulfhydryl groups, which are later re-oxidized to form new disulfide bonds in a straightened position.
• Protein Denaturation occurs as the high alkalinity and chemical action disrupt the delicate folding of keratin proteins. This alteration to the protein’s natural shape contributes to the hair’s softened state, allowing it to be physically straightened with combs or brushes during the process.
• Cuticle Lifting and Damage are almost inevitable. The cuticle, the hair’s outermost protective layer of overlapping scales, must be lifted for the chemicals to reach the cortex. This lifting, combined with the strong alkaline environment, can cause the cuticle scales to become irregular, porous, or even chip away. A compromised cuticle means the hair is less protected from external aggressors and prone to moisture loss.

The duration the relaxer remains on the hair is critical. Leaving it on for too long, or using too strong a formulation, can lead to severe damage, sometimes described as the hair turning to a “mushy paste”. This indicates extreme degradation of the protein structure, a point of no return for the hair’s integrity.

Relaxers fundamentally alter hair’s protein structure by breaking and reforming bonds, making hair more susceptible to damage.

What Does Hair Lose in the Process?

The most immediate and significant loss for relaxed hair is a reduction in its Tensile Strength. Tensile strength is the hair’s ability to withstand stretching and pulling before breaking. Studies consistently show that relaxed hair has significantly lower tensile strength compared to virgin, untreated hair. This reduction is a direct consequence of the broken and altered disulfide bonds, which are the primary contributors to hair’s mechanical strength.

Consider a study where hair samples treated with sodium hydroxide relaxer showed a reduction in tensile strength compared to untreated hair. Another study found that cosmetic treatments, including permanent hair relaxers, produced increasingly greater reductions in tensile strength, with relaxed hair having a lower average tensile strength than untreated hair. This diminished strength makes relaxed hair more susceptible to breakage from everyday styling, combing, and environmental stressors.

Beyond mechanical strength, relaxed hair also experiences changes in its amino acid composition and overall protein integrity. Research has documented a decrease in the amino acid Cystine (the building block of disulfide bonds) in relaxed hair compared to natural hair. This reduction in cystine levels is a clear indicator of the extent of structural modification. Some studies have even likened the cystine levels in damaged relaxed hair to those found in genetic hair fragility disorders like trichothiodystrophy.

The hair’s ability to retain moisture is also compromised. With a damaged cuticle and altered internal structure, relaxed hair often becomes more porous, meaning it absorbs and loses water more readily. This increased porosity can lead to chronic dryness and brittleness, further contributing to breakage.

Relay

The journey of understanding relaxers extends beyond the immediate chemical reaction to encompass the broader implications for hair health, the science of recovery, and the historical currents that shaped their use. To truly comprehend the scope of what happens to hair’s protein structure with relaxers, we must consider the intricate interplay of chemical alteration, the body’s response, and the cultural narrative woven around these powerful products.

Can Hair Ever Truly Recover Its Original Structure After Relaxing?

The fundamental answer lies in the type of relaxer used. For hydroxide-based relaxers, the chemical alteration is irreversible. The disulfide bonds are not merely broken and then reformed; they are permanently converted into lanthionine bonds.

This means the sections of hair that have undergone lanthionization will never revert to their original curl pattern or protein architecture. New hair growth from the scalp will, of course, retain its natural texture, but the chemically treated lengths remain permanently altered.

With thioglycolate relaxers, the situation is slightly different. These systems rely on a two-step process ❉ reduction followed by oxidation. While the disulfide bonds are broken in the first step, they are theoretically reformed in the second step in the hair’s new, straightened configuration. However, even with proper neutralization, the process is not without its costs.

Hair treated with thioglycolates can still experience protein loss and structural changes, particularly in Afro hair, as one study indicated that the use of thioglycolate did not result in additional loss of protein or tryptophan, except in Afro hair. The delicate balance required for complete bond reformation is often imperfect, leaving the hair compromised.

The concept of “recovery” for relaxed hair often refers to improving its condition, not reversing the chemical change. This involves strategies to replenish lost proteins, restore moisture, and fortify the compromised hair shaft. Protein Treatments, for instance, aim to supplement the hair with hydrolyzed proteins that can temporarily coat the hair strands, offering some external strength and elasticity.

These treatments, while beneficial for mitigating some of the damage, do not rebuild the original disulfide bonds or reverse lanthionization. They act more as a temporary scaffolding for weakened strands.

Consider the ongoing challenge of managing chemically altered hair. The repeated application of relaxers to new growth means that older sections of hair accumulate damage over time. This leads to a demarcation line where the natural hair meets the relaxed hair, creating a fragile zone prone to breakage. This continuous cycle of chemical application on already weakened hair compounds the structural integrity issues.

What Are the Less Discussed Impacts on Hair Fiber Integrity?

Beyond the obvious breakage of disulfide bonds, relaxers induce a cascade of less visible, yet equally significant, changes to the hair fiber. These alterations contribute to the overall fragility and altered behavior of relaxed hair.

• Oxidative Alterations and Side-Chain Dehydration ❉ Studies have shown that hair exposed to sodium hydroxide can exhibit increased oxidative alterations and dehydration of amino acid side chains. This indicates a broader chemical assault on the hair’s molecular components, not just the disulfide bonds.
• Changes in Hair’s Hygroscopic Properties ❉ Relaxed hair often experiences reduced water uptake and retention. This is linked to the disruption of the hair’s internal structure and cuticle integrity, making it harder for the hair to maintain its optimal moisture balance. This contributes to chronic dryness and brittleness.
• Altered Amino Acid Composition ❉ While cystine reduction is well-documented, other amino acids like citrulline and arginine have also been found to decrease in relaxed hair. These amino acids play roles in hair’s overall health and mechanical properties. The alteration in their levels points to a systemic change in the hair’s protein makeup.
• Impact on Hair Cortex Density ❉ Some research, observed through electron microscopy, has even noted an increase in the density of the intermacrofibrillar matrix in the cortex of chemically treated hair. While the full implications of this are still being understood, it suggests a compaction or rearrangement of internal structures, which could affect flexibility and strength.

The cumulative effect of these microscopic changes is a hair fiber that is fundamentally different from its natural state. It is not simply straightened; it is chemically transformed, with a compromised internal architecture that impacts its long-term health and resilience.

Relaxers cause irreversible changes to hair’s core protein structure, leading to reduced strength and altered moisture dynamics.

The Societal Mirror and Scientific Inquiry

The widespread use of relaxers, particularly among Black women, is intertwined with historical beauty standards and societal pressures. For generations, straight hair was often presented as the ideal, influencing perceptions of professionalism, manageability, and beauty. This cultural context is vital when discussing the science of relaxers, as it highlights the complex choices individuals navigate regarding their hair.

While the cosmetic benefits of relaxers have been clear, scientific inquiry has increasingly brought to light potential health implications beyond immediate hair damage. Beyond the well-known issues of scalp burns, hair loss, and breakage, more recent studies have explored links between relaxer use and systemic health concerns.

A compelling, and indeed controversial, data point comes from a 2015 study published in the Journal of Cosmetic Science by França-Stefoni et al. This research evaluated protein loss in hair from combined chemical treatments (dye and relaxer) using the bicinchoninic acid (BCA) method. The study found that when dark brown curly Caucasian hair was subjected to both dyeing and straightening with a sodium hydroxide-based relaxer, there was a staggering 356% Increase in Protein Loss Relative to Virgin Hair.

This specific statistic, while on Caucasian hair, offers a powerful illustration of the extreme protein degradation that can occur, far exceeding the impact of either treatment alone. It underscores the profound chemical stress hair undergoes and the extensive molecular changes beyond mere bond breakage.

Such data prompts deeper reflection on the cumulative impact of chemical treatments. The long-term health effects of relaxers continue to be an area of active investigation, with some research suggesting associations with certain hormone-related cancers, such as uterine and ovarian cancer, particularly with frequent and long-term use. While the precise mechanisms are still being elucidated, the potential for chemical absorption through the scalp, especially when compromised by burns or irritation, raises valid concerns.

The dialogue surrounding relaxers has shifted considerably with the rise of the natural hair movement. This movement has brought greater awareness to the beauty and versatility of natural textures, encouraging a re-evaluation of historical beauty standards and the choices made regarding hair care. It has also spurred a demand for more gentle and hair-supporting products, recognizing the intrinsic value of hair health over purely aesthetic alterations.

Reflection

To truly understand hair’s protein structure after a relaxer application is to peer into a microcosm of chemical transformation, cultural resonance, and personal choice. The once tightly coiled or wavy strands, meticulously held by intricate disulfide bonds, undergo a profound, often irreversible, alteration. The scientific journey into this change reveals a landscape of broken and reformed connections, a hair fiber forever changed in its very essence.

Yet, this understanding is not merely about identifying damage; it is an invitation to appreciate the resilience that remains, the possibilities for care, and the profound significance hair holds in our lives. As we continue to learn, the quiet wisdom of our strands speaks volumes, guiding us toward choices that honor both science and self.

References

• Robbins, C. R. (2012). Chemical and Physical Behavior of Human Hair. Springer Science & Business Media.
• Dawber, R. P. R. & Van Neste, D. (2002). Hair and Scalp Disorders ❉ Common Problems and Their Management. CRC Press.
• Baden, H. P. & Goldsmith, L. A. (1988). The Structural Proteins of Hair. Springer-Verlag.
• Khumalo, N. P. et al. (2010). ‘Relaxers’ damage hair ❉ Evidence from amino acid analysis. Journal of Cosmetic Dermatology, 9(2), 148-151.
• Shetty, V. K. et al. (2013). Hair cosmetic practices and their effects on hair and scalp in women. Indian Journal of Dermatology, 58(2), 108-113.
• França-Stefoni, C. et al. (2015). Protein loss in human hair from combination straightening and coloring treatments. Journal of Cosmetic Science, 66(5), 329-338.
• Leite, L. A. & Maia Campos, P. M. B. G. (2017). Impact of acid (“Progressive Brush”) and alkaline straightening on the hair fiber ❉ Differential effects on the cuticle and cortex properties. Journal of Cosmetic Science, 68(1), 10-21.
• Sanad, R. A. et al. (2019). Clinical and dermoscopic evaluation of the effect of keratin hair straightening on curly hair. Journal of Cosmetic Dermatology, 18(6), 1832-1837.
• Olsen, E. A. et al. (2011). Hair care practices associated with central centrifugal cicatricial alopecia. Journal of the American Academy of Dermatology, 64(1), 87-93.
• Hatsbach de Paula, J. N. & Basílio, F. M. A. (2022). Effects of chemical straighteners on the hair shaft and scalp. Anais Brasileiros de Dermatologia, 97(2), 193-203.