The hair care industry is rife with ingredient claims, ranging from transformative benefits to potential harm. For cosmetic chemists and formulators, understanding the validity of these assertions is critical to developing effective and scientifically sound products. This article examines some of the most prevalent claims surrounding ingredients and hair health, presenting both supporting insights and counter-arguments from industry experts to provide a balanced perspective on their true impact.
This article is only available to registered users.
Log In to View the Full Article
The hair care industry is rife with ingredient claims, ranging from transformative benefits to potential harm. For cosmetic chemists and formulators, understanding the validity of these assertions is critical to developing effective and scientifically sound products. This article examines some of the most prevalent claims surrounding ingredients and hair health, presenting both supporting insights and counter-arguments from industry experts to provide a balanced perspective on their true impact.
Sharing their expertise are:
- Linda Foltis, an industry consultant who most recently served as vice president of R&D and regulatory at Function of Beauty until 2023. There, she established thought leadership in personalized hair care.
- Perry Romanowski is a cosmetic scientist and vice president of the consulting firm Element 44 Inc. He has spent more than two decades creating products to solve consumer problems, including 16 years at Alberto-Culver, where he led the development of innovative hair care.
- Peter Bailey, Ph.D., an industry consultant and FMCG R&D executive with a 30-year track record of launching new technologies in highly differentiated and impactful products including leading Unilever beauty brands Dove, Tresemme, Sunsilk, Clear and TIGI.
‘Bad’ Hair Color Ingredients
1. P-Phenylenediamine (PPD)
Claims: PPD is one of the most common and potent allergens in permanent hair dyes, especially in darker shades; it can cause severe allergic reactions, skin and eye irritation; it also has potential links to cancer.
Expert insights:
“PPD in oxidative hair dye systems has 100× more affinity to hair than skin,” Foltis writes. After application, most of what is not absorbed by hair is rinsed out.” She adds that PPD patch testing is recommended to reduce allergic reactions. What’s more, exposure time to PPD oxidative hair dye systems is generally limited to 15-45 min per application. “PPD has excellent grey hair coverage and provides long-lasting natural-looking hair color shades,” she explains.
“While there is concern that PPD causes allergic reactions, the industry acknowledges and screens for this with patch-testing guidance,” Romanowski agrees. “The presence of an allergen does not mean the ingredient is unsafe in general use, it means it is unsafe for a subset of individuals who become sensitized.” Per Romanowski, the key regulatory bodies, including those in the EU – where ingredient scrutiny is more stringent than in the U.S. – allow PPD at controlled levels because the overall risk is well-characterized and manageable.
“As for cancer claims, large epidemiological reviews have not shown consistent or convincing evidence linking oxidative hair dyes to cancer in humans,” Romanowski continues. “PPD remains essential for achieving permanent, durable color and when used as directed, it has an extensive safety record.”
Bailey concurs, "While PPD is a well‑known allergen, it remains one of the most effective and tightly regulated oxidative dye precursors, and adverse reactions are rare when products are used as directed." He adds that modern formulations use controlled concentrations, stabilizers and antioxidant systems to minimize sensitization risk.
What's more, per Bailey, mandatory patch testing further reduces the likelihood of reactions. "Regulatory bodies worldwide continue to permit PPD because, when properly formulated and applied, it delivers reliable color performance with an acceptable safety margin."
2. Resorcinol
Claims: Resorcinol is a common dye ingredient used to achieve a final color; it can cause skin irritation and allergic reactions and is a suspected endocrine disruptor.
Expert insights:
“Resorcinol is a key ‘coupler,’ reacting with a primary dye intermediate such as PPD, creating a larger molecule in the hair shaft that prevents color wash out and contributes to [the] final hair color shade,” Foltis writes. “Resorcinol has 200× more affinity to hair than skin,” Foltis emphasizes.
“Resorcinol can cause irritation in its raw form, but irritation potential is significantly reduced when it’s part of an oxidative dye system and used at proper levels,” Romanowski explains. “The endocrine disruption claim is often repeated, but that is based on high-dose animal data that does not match human cosmetic exposures.
“In actual hair dye formulas, concentrations are tightly controlled and the ingredient is rinsed away after processing, which further limits exposure,” he continues, adding that while regulatory agencies continue to review resorcinol safety, they have not banned it because the real-world risk remains low when used as intended.
"Although resorcinol can cause irritation in high concentrations, its use in hair color is strictly limited and monitored by global regulators, with safety assessments confirming that controlled levels in oxidative dyes do not pose systemic risk," Bailey writes.
"The 'endocrine disruptor' concern stems largely from high-dose animal studies that do not reflect cosmetic exposure," Bailey continues. "In real-world use, resorcinol remains an effective dye coupler with a long history of safe application when used within regulated limits."
3. Ammonia (Ammonium Hydroxide)
Claims: Ammonia is used to open the hair cuticle so the color can penetrate the hair shaft; it causes a strong, pungent smell that can irritate the eyes, nose and respiratory system; it also can cause scalp irritation and leave hair dry, brittle and damaged over time.
Expert insights:
“Ammonia is used in permanent hair color to swell the hair fiber and allow the dye molecules and hydrogen peroxide to penetrate and react inside the hair shaft efficiently,” Foltis shares. “[This enables] the transformation of hair color in less than 45 minutes.” She adds that ammonia enables excellent color coverage for grey and resistant hair – and highlights how exposure to hair and scalp is low due to the ingredient’s volatility and rinseability.
“People are wary of ammonia because of its awful odor, not because it is uniquely toxic,” Romanowski writes. “Its role is simple and effective, raising the pH so dyes can penetrate the hair.” He, too, emphasizes that when ammonia is used at the levels found in hair color, it does not create long-term health risks and it evaporates quickly during processing.
“As far as hair damage goes, in practice, ammonia formulas can actually be less damaging than ammonia-free alternatives because they rinse more cleanly and do not linger in the hair,” he explains.
Bailey also highlights how ammonia’s strong smell often drives negative perception, "but it is one of the most efficient and predictable alkalizing agents for permanent color, allowing precise pH control and consistent grey coverage."
He also explains that the volatility of ammonia means it dissipates quickly during application, reducing prolonged scalp exposure. "When used at regulated levels, ammonia does not inherently damage hair; rather, damage is more closely linked to oxidative processing itself, which occurs regardless of whether not ammonia is used."
4. Ethanolamines (MEA, DEA, TEA)
Claims: Ethanolamines are often used as an ammonia substitute in "ammonia-free" products; these can still cause damage to the hair shaft and scalp irritation (dermatitis); they also may be toxic to skin cells.
Expert insights:
“Most brands are using MEA,” Foltis observes. “[It is] milder on hair and skin than ammonia and provides good color coverage for most hair types. [It is] an excellent alkalizer for demi-permanent hair color formulations.”
“The irritation potential of ethanolamines is well-known but manageable within regulated use levels,” Romanowski concedes. “Claims about cell toxicity, [however], usually come from in vitro studies that use concentrations way higher than what appears in finished products.”
Bailey affirms that while ethanolamines can cause irritation at high concentrations, they are often milder on the scalp than ammonia and provide longer processing windows for controlled color development.
"Hair damage concerns typically arise from overuse or excessive alkalinity, not the molecule itself. Modern formulations balance MEA with conditioning agents and buffering systems to minimize cuticle swelling and maintain hair integrity."
5. Formaldehyde and Formaldehyde-releasing Agents
Claims: Formaldehyde and formaldehyde-releasing agents (e.g., DMDM hydantoin, quaternium-15, etc.) are used as preservatives; formaldehyde is a known human carcinogen and a potent allergen that can trigger or worsen contact dermatitis and skin irritation.
Expert insights:
“Today, formaldehyde donor preservatives are restricted in use level and product formats,” Foltis explains. “They are highly effective, at low use levels, in providing broad-spectrum preservation across a pH range of 3-8.
“DMDM hydantoin has a slower formaldehyde release profile compared to quaternium-15,” she continues, adding that DMDM hydantoin has excellent performance in shampoos at low use levels, supporting mass market formulations. “Formaldehyde donors are typically formulation friendly, not impacting clarity, viscosity or product performance.”
However, according to Foltis, formaldehyde-releasing agents used in hair straighteners are employed at high levels (2-12%), where formaldehyde is released during the flat iron process. “[This can release] formaldehyde and result in irritation and stress on the respiratory system during treatment,” she explains. In terms of hair color, Foltis highlights these ingredients may shift it toward a brassy hue. In addition, they may cause supercontraction of the hair shape.
“These ingredients have been used in cosmetic products for decades without causing significant harm,” Romanowski emphasizes. “Formaldehyde releasers used as preservatives release only tiny, controlled amounts to prevent microbial growth, and finished product levels are far below occupational exposure limits.
“The cancer hazard associated with formaldehyde stems from high-dose inhalation in industrial settings, not from incidental cosmetic exposure,” he continues. Per Romanowski, allergic reactions can occur in sensitized individuals, which is why regulations require the disclosure of these ingredients, why there are maximum use levels, and why companies continually work toward alternative preservative systems.
“For most consumers, the benefits of a safe, preserved product outweigh the minimal exposure risk,” he adds.
Bailey reiterates that formaldehyde itself is tightly restricted in cosmetics, and formaldehyde‑releasing preservatives are designed to release only trace amounts necessary for microbial protection.
"When used within regulatory limits, these materials provide effective preservation with low exposure risk, and many have decades of safe use supported by toxicological data," he explains. "Alternatives exist, but they may introduce their own sensitization or stability challenges, so formulators need to choose preservatives based on overall safety and performance."
‘Bad’ Preservatives, Solvents and Stabilizers
6. Parabens
Claims: Parabens (e.g., propylparaben, butylparaben, etc.) are used as preservatives to prevent microbial growth; they can mimic the activity of the hormone estrogen and are suspected endocrine disruptors, potentially linked to reproductive issues and breast cancer.
Expert insights:
“Parabens are rarely used in hair care formulations today, as more progressive preservative systems have proven to provide adequate protection in most formulations,” Foltis writes.
Romanowski notes, “These are one of the most-studied preservative types in cosmetics, and the weight of evidence consistently shows that they are safe at cosmetic use levels.” He explains that while they can bind weakly to estrogen receptors, their activity is “thousands of times lower than natural estrogen and nowhere near the levels required to meaningfully disrupt human physiology.”
“Epidemiological studies have not demonstrated causal links to breast cancer or infertility,” Romanowski continues. “Regulatory agencies around the world, including those with the strictest standards, continue to allow parabens because their real-world exposure is low, predictable and well within safety margins.” And here again, according to Romanowski, paraben alternatives can unfortunately carry higher irritation or sensitization risks and can make consumers less safe.
Bailey weighs in: "Parabens have been extensively studied and consistently shown to be safe at permitted levels, with weak estrogenic activity far below that of naturally occurring phytoestrogens found in foods (there is a higher concentration in blackberries, for example, than is allowed in cosmetics)."
He underscores that they remain some of the most effective broad‑spectrum and low‑sensitizing preservatives available. "Regulatory agencies worldwide continue to support their use because they offer strong microbial protection with minimal irritation risk compared to many 'natural' alternatives."
7. Alcohol
Claims: Alcohols can cause hair dryness and lead to brittle, dehydrated hair.
Expert insights:
Thanks to VOC regulations, alcohol use levels in hair care formulations have decreased significantly, per Foltis. She highlights, though, the importance of knowing the two types of alcohol that are used.
“Short-chain alcohol such as ethanol (denatured alcohol) is volatile [and] typically used in styling formulations to reduce tack and improve dry times in hair setting. Short-chain alcohol is also used as a vehicle to aid [in the] penetration of active ingredients for hair health.
“Long-chain alcohols, fatty alcohols, are used in hair conditioners and cream stylers,” she continues. “[They] provide conditioning benefits to hair such as slip, softening and frizz reduction.
Romanowski concurs: “Short-chain alcohols like ethanol can be drying at high levels but in hair products, they function as solvents, evaporate quickly and do not remain on the hair long enough to cause meaningful damage.”
Bailey also highlights that not all alcohols behave the same. "[S]hort‑chain alcohols such as ethanol can be drying in high concentrations, but they also improve ingredient penetration, reduce drying time, and enhance product performance."
He continues, "Many hair products use longer chain fatty alcohols (cetyl, stearyl), which are actually conditioning and help soften and smooth the hair. Dryness is formulation‑dependent, not an inherent property of 'alcohol' as a category."
8. Fragrance (Parfum)
Claims: The collective term fragrance can hide mixtures of dozens of undisclosed chemicals including phthalates that are known endocrine-disrupting chemicals linked to hormonal interference and developmental issues. Fragrances are also a major source of allergic reactions and skin/respiratory irritation.
Expert insights:
“Fragrance labeling now requires disclosing allergens,” shares Foltis. “Fragrance has [also] advanced from covering formulation bases and providing a nice smell, to providing a sensory experience,” she adds. “Fragrance can be used to enhance mood, boost well-being and mask pollution odors that attract to hair.”
“Fragrances are a mixture of ingredients, but that does not make them inherently unsafe,” Romanowski explains. “The industry follows [International Fragrance Association] (IFRA) standards, which restrict or prohibit materials based on rigorous safety assessments.”
He notes that while fragrances can cause allergic reactions in a small portion of the population, the primary allergens must be disclosed on the label so that affected individuals can avoid exposure. “Fragrances continue to be included because that’s what consumers want to buy,” he writes.
"While fragrance can trigger irritation in sensitive individuals, it plays a key role in consumer experience and product acceptance," Bailey emphasizes. "Modern fragrance design follows strict IFRA guidelines, and many brands offer fragrance‑free options for those with sensitivities."
He additionally notes that the presence of "undisclosed chemicals" reflects proprietary blends, not hidden hazards, and safety assessments ensure that all components meet regulatory and toxicological standards.
9. Sulfates
Claims: Sulfates including sodium lauryl sulfate (SLS) and sodium laureth sulfate (SLES) are harsh detergents and surfactants; they can strip hair color, cause skin and eye irritation, and may worsen conditions like dermatitis and eczema on the scalp. SLS insult on the scalp also indirectly impacts follicular health.
Expert insights:
“Sulfate surfactants have excellent cleansing properties, [are] efficient in use and are cost-effective, enabling mass market shampoo formulations,” Foltis observes, adding, “most shampoos today have shifted to ethoxylated sulfates such as sodium laureth sulfates.”
However, per Foltis, sulfate-free formulations are not as efficient as their sulfated counterparts. “[They] typically require higher surfactant levels and more effort in foam profile management.” She adds they are also more difficult to preserve and create overall more expensive formulations.
Romanowski takes a step back: “Sulfates work to clean surfaces. The idea that they are inherently harsh ignores the importance of formulation. ... Finished products contain conditioning agents, polymers, co-surfactants and pH adjustments that reduce irritation and improve mildness.”
According to Romanowski, yes, at high concentrations, SLS can be irritating; “but consumers are not using pure SLS on their scalp,” he writes. “SLES, the ethoxylated version, is significantly milder and widely used in shampoos with good tolerance. Claims that sulfates cause or worsen eczema over-simplify a condition that is highly influenced by genetics, environment and the overall formula rather than one ingredient,” he concludes.
"Sulfates are highly effective cleansers with decades of safe use and are not inherently damaging when formulated with conditioning agents and used appropriately," Bailey notes, reiterating that SLES, in particular, is milder due to ethoxylation.
"...[I]rritation is more closely linked to concentration and exposure time than the ingredient itself," he continues. "For many consumers, sulfates provide the best balance of cleansing, foaming and rinseability. In addition, sulfate-free surfactants are not in themselves inherently milder – in some cases, they can be harsher than sulfates."
Other ‘Bad’ Ingredients
10. Hydrogen Peroxide
Claims: Hydrogen peroxide is used for bleaching properties in permanent dyes; it can cause moisture loss, dryness, cuticle damage and scalp irritation, leading to hair breakage.
Expert insights:
“While the damage to hair is duly noted, hydrogen peroxide is a key component in hair bleaching and hair coloring processes,” Foltis emphasizes, adding: “hydrogen peroxide boosted by persulfates can lighten hair by seven shades!”
Romanowski concurs. “While this is true, when used at proper levels, [hydrogen peroxide] breaks down into water and oxygen, and leaves no long term residue. Hair conditioners, bonding treatments and controlled processing significantly mitigate the damaging effects of peroxide.”
In addition, he notes there is no suitable alternative that works better. “[S]o if consumers want to change the color of their hair, there is little else they can do than be exposed to this ingredient.”
Bailey agrees that hydrogen peroxide is essential for oxidative coloring and lightening, adding that it is well-studied and, when used at controlled concentrations, it is predictable and effective.
"Hair damage results primarily from the chemical process of melanin oxidation, not peroxide alone, and modern formulations incorporate conditioning polymers, oils and pH buffers to mitigate dryness and maintain structural integrity," Bailey explains.
11. Heavy Metals
Claims: Heavy metals are sometimes found as contaminants; they are used specifically in "progressive" darkening dyes and linked to neurotoxicity and developmental issues.
Expert insights:
“Advancements in analytical tools and methods, followed by manufacturing processes, have shown significant progress in reducing heavy metals in cosmetic ingredients,” assures Foltis.
“The overwhelming majority of permanent hair color formulations do not contain intentional heavy metals,” Romanowski explains. “Modern regulations tightly control allowable levels and reputable manufacturers test raw materials to ensure compliance.” He highlights it would also not be economically feasible or possible to remove all traces of heavy metals from these products.
Bailey also notes how heavy metals are strictly regulated, and that reputable manufacturers test raw materials to ensure levels remain within safe, technically unavoidable limits.
"Contamination risks are well-understood and managed through supplier controls, purification steps, and routine analytical testing," he writes. "When present at trace levels, heavy metals do not pose meaningful health risks in cosmetic use."
12. Organic Solvents
Claims: Organic solvents are used in some hair dyes; they are potential neurotoxins and linked to allergic reactions; in high doses, they can cause potential issues during pregnancy.
Expert insights:
“This is a big category of ingredients and they are not all the same,” Romanowski remarks. “However, cosmetic formulas use solvents at low concentrations, and they are rinsed after processing. Safety assessments take vulnerable populations, including pregnant individuals, into account.”
He emphasizes that, as with most ingredients, the dose and exposure route matter far more than the name of the ingredient group.
"Organic solvents used in hair color are selected for their ability to dissolve dye intermediates and ensure even color development," Bailey explains. "Exposure levels in cosmetic products are far below those associated with systemic toxicity, and safety assessments confirm their suitability when used within regulated limits."
Bailey additionally notes that formulators also increasingly use solvent blends to reduce irritation and improve scalp comfort.
13. Silicone
Claims: Silicone can cause build-up on hair and weigh it down over time; it also negatively impacts the environment.
Expert insights:
“Silicones have many benefits on hair,” writes Foltis. “They add shine via contrast and enhance specular reflectance of light on hair through film formation.” She notes they also enhance combing/detangling, provide anti-frizz benefits by sealing the cuticle, and protecting hair from humidity. Additionally, they protect hair from thermal and mechanical insults during hair styling.
“While silicones have developed a poorer reputation than when I first started, they remain some of the most effective conditioning materials available,” Romanowski comments. “Replacements just do not work as well. Build-up depends on the type of silicone, the formula and how the consumer uses it.” Per Romanowski, most silicones are water dispersible or easily removed with standard shampoos.
“As far as the environment goes, silicones are inert, non-bioaccumulative and are allowed by global regulators. For many consumers, the performance benefits outweigh the perceived drawbacks.”
As Bailey explains, silicones do not damage hair; they form lightweight, protective films that reduce friction, enhance shine and minimize breakage. "Build‑up concerns are largely outdated, as modern silicones vary widely in volatility and solubility." He notes that most shampoo silicones are very high-viscosity gums that give a dry, slippery feel; and many rinse cleanly from the hair during washing.
"Environmental concerns are being addressed through improved biodegradability and alternative silicone technologies," he adds.
‘Good’ Ingredients for Hair
14. Natural Colorants
Claims: Natural colorants can be used as a base for less chemically aggressive hair colors, often replacing harsher synthetic dye intermediates like PPD and resorcinol.
Expert insights:
“Natural colorants have progressed in hair dye formulations, but as of today, they do not have the grey coverage or the color palette of currently approved synthetic hair dye ingredients,” observes Foltis.
“Sure, these are usually less aggressive but that’s because they just don’t work as well,” Romanowski writes. “That’s why they haven’t replaced oxidative dyes. If someone wants real, lasting color, natural dyes won’t get you there.” He also cautions that natural does not automatically mean safer, and many botanicals contain allergens and irritation risks.
"Natural colorants can be gentler but often lack the performance, shade range and longevity of oxidative dyes," Bailey reiterates. "They may still cause allergies (e.g., henna), and their 'natural' status does not guarantee safety or consistency."
As an alternative, per Bailey, many consumers use natural colorants as a complementary option rather than a full replacement for synthetic systems.
15. Moisturizing Oils, Butters and Humectants
Claims: Moisturizing oils, butters and humectants (e.g., argan, coconut, etc.) help to counteract the dryness and damage that can occur during coloring by moisturizing the hair shaft and soothing the scalp; they also provide nourishing properties, leaving hair shiny and soft.
Expert insights:
“[However, these ingredients] can result in formulation stickiness, adding drag,” Foltis notes. “Many of the natural butters and oils [also] have a shorter shelf life and they can impact formulation color.”
“These ingredients certainly make hair feel nicer, but they cannot undo the structural changes caused by oxidative coloring,” Romanowski explains. “Most of the shine and softness they deliver is temporary surface conditioning, not true repair. And honestly, they don’t work as well as silicones.”
Bailey chimes in, "While beneficial for conditioning, oils and butters can interfere with color uptake, reduce dye penetration or weigh hair down if overused." He also emphasizes that their performance varies widely depending on molecular size and formulation context.
"They are valuable supportive ingredients but not a substitute for controlled chemical processes in coloring," he concludes.
16. Strengthening Proteins, Extracts and Vitamins
Claims: Strengthening proteins, extracts and vitamins (e.g., keratin, biotin, vitamin E and hyaluronic acid) work to fortify the hair structure and promote overall hair and scalp health; they deeply moisturize and improve elasticity; they provide antioxidant protection and support healthy hair growth; and they reduce breakage and frizz.
Expert insights:
“[These] tend to be expensive,” counters Foltis, adding “many formulations do not employ these actives at performance levels.” She adds that they, too, have a shorter shelf-life.
“I’m skeptical that a consumer would notice any significant difference in their hair with the use of these types of ingredients,” Romanowski chimes in. “Cosmetic product makers essentially add ingredients like these more for the stories than for any real impact they will have.”
He notes there is a problem with them in terms of both cost and effectiveness. “Extracts, vitamins and hydrolyzed proteins are mostly added at small levels so marketers can talk about them, not for what the ingredients do in the formula.”
Bailey agrees that proteins are often included in formulations more for marketing claims than any significant functional benefit. In addition, the large molecular weight of proteins such as keratin often preclude their penetration into the hair fiber in any meaningful level — "unless they undergo significant hydrolysis into smaller peptide fragments," he notes.
However, he reverts to the view that extracts and vitamins such as biotin and vitamin E are primarily used to support marketing claims, having "little or no functional or consumer-perceptible performance."
