The study, led by Aaliyah Bourne of Florida State University College of Medicine together with Victoria Palmer of SUNY Downstate Health Sciences University and Amy McMichael of Wake Forest University School of Medicine, examined 31 conditioners explicitly marketed for textured, coily, curly, or natural hair. The products were drawn from the 20 conditioner brands most frequently mentioned by Black consumers in Mintel’s Black Haircare–US–2024 report, and the final sample comprised 13 deep conditioners and 18 leave-in formulations across 18 brands. Rather than testing products in a laboratory, the researchers systematically decoded ingredient labels, classifying every declared ingredient using the European Commission’s CosIng database and International Nomenclature of Cosmetic Ingredients naming conventions, then cross-referencing the lists against three published safety frameworks.

Those frameworks were chosen with clinical precision. The American Contact Dermatitis Society’s 2020 Core Allergen Series represents the contact allergens most frequently identified through patch testing in dermatology clinics. Two additional chemical-of-concern lists, one covering endocrine-disrupting and asthma-associated chemicals in consumer products generally and one focused specifically on hair products used by Black women, rounded out the screen. The authors are careful to frame the results as hazard identification rather than risk estimation: cosmetic labels disclose the order of ingredients but never their concentrations, and sensitization depends on dose and cumulative exposure. Still, the pattern that emerged is striking. Every single one of the 31 products contained at least two label-declared chemicals of concern or allergens, with a mean of 5.9 per formulation and a range extending as high as 10.

On the functional side, the analysis revealed meaningful differences between product categories that marketing does not advertise. Deep conditioners contained higher densities of quaternary ammonium conditioning agents, averaging 2.6 per product compared with 2.3 in leave-ins, and substantially more culturally relevant emollients such as coconut oil and shea butter, at 5.3 versus 3.3 per product. These cationic surfactants adsorb to the negatively charged hair cuticle, reducing friction and improving mechanical resilience, while lipid-rich emollients replenish the moisture barrier. Leave-in conditioners, by contrast, more frequently incorporated silicones, present in 66.7 percent of leave-ins versus 53.8 percent of deep treatments, with dimethicone and amodimethicone the most common. Silicones excel at frizz reduction and surface protection during daily styling, though cumulative deposition in low-porosity, tightly coiled hair may eventually impair moisture penetration and require periodic clarification.

One of the most clinically significant findings concerns hydrolyzed proteins. Protein reinforcement is a commonly cited rationale for using deep conditioning treatments, particularly for patients with chemically processed hair or significant weathering damage, in which structural protein loss is central to the pathology. Yet the study found hydrolyzed proteins in fewer than a quarter of products in both categories, 23.1 percent of deep conditioners and 22.2 percent of leave-ins, with low ingredient density and no single protein source predominating. The formulation data simply do not support the assumption that a deep conditioning designation implies protein delivery. Patients who rely on category labeling rather than ingredient review may end up with products that fail to address their therapeutic need, a gap the authors argue should be closed through ingredient-level counseling.

The safety screen also distinguished between ingredients that are ubiquitous but clinically minor and those that are less common but far more actionable. Fragrance, declared in 93.5 percent of products, cetearyl alcohol at 87.1 percent, phenoxyethanol at 58.1 percent, and benzyl alcohol at 41.9 percent topped the prevalence list, but all are relatively infrequent causes of allergic contact dermatitis. Of greater concern, stearamidopropyl dimethylamine, the amidoamine hapten carried on the ACDS Core Allergen Series, appeared in 38.7 percent of products, and the preservatives methylisothiazolinone and methylchloroisothiazolinone each appeared in 12.9 percent. Methylisothiazolinone was the second most frequently positive allergen in the most recent North American Contact Dermatitis Group patch test series, positive in 13.8 percent of tested patients. Because both the amidoamine and the isothiazolinones appear under names that give no hint of allergenic potential, neither is likely to be recognized as a hazard without deliberate ingredient review.

Exposure patterns differ between the two formats in ways that matter for counseling. Leave-in conditioners remain on the hair and scalp between washes, and daily application increases cumulative allergen exposure, raising the likelihood of both sensitization and elicitation in predisposed individuals. Deep conditioners are rinsed out, but common application practices such as heat cap or steam treatments may enhance percutaneous absorption of sensitizing ingredients during the treatment window. Fragrance poses a particular counseling problem because proprietary blends are permitted under a single composite disclosure of fragrance or parfum under current FDA labeling regulations, preventing both patients and clinicians from assessing the true allergen burden. The authors also caution that marketing language such as clean or natural is not standardized and provides no reliable signal of formulation quality.

Beyond chemistry, the study documented an economic and logistical burden that compounds the safety concerns. Per-ounce pricing across the sample ranged from $0.41 to $7.09, with a mean of $1.64 per ounce, against a national shampoo and conditioner benchmark of $0.44 per ounce derived from Mintel market data. A striking 83.9 percent of products were classified as significant premium, costing more than 50 percent above the national per-ounce average, and only a single product, 3.2 percent of the sample, fell into the accessible tier. Retail availability was similarly constrained: 51.6 percent of products were listed on only one or two of the five major platforms assessed, earning a poor accessibility rating, while just 32.3 percent were available on four or five platforms. These findings echo prior documentation of a minority hair tax, in which ethnic haircare products carry systematic pricing bias.

The practical consequences of this dual burden are straightforward. Patients who cannot reliably afford recommended products may substitute cheaper alternatives with less favorable ingredient profiles or abandon their regimens altogether, undermining the preventive dermatologic care that conditioning provides. Limited retail availability compounds the barrier, particularly for patients in rural or underserved communities without access to specialty beauty retailers. The authors argue that dermatologists are well positioned to bridge the gap by offering ingredient-level guidance that accounts for formulation composition, sensitization risk, cumulative exposure patterns, and access constraints, rather than defaulting to product category labels or marketing claims. For patients with existing scalp conditions, suspected allergic contact dermatitis, or atopic predisposition, that level of specificity may make the difference between a workable regimen and chronic irritation.

The study’s limitations temper but do not erase its conclusions. Ingredient concentrations are proprietary and undisclosed, so the analysis identifies hazards without quantifying risk, and most users of these products will never develop allergic contact dermatitis. The sample was small and intentionally limited to mass-market brands with documented cultural relevance to Black consumers, excluding salon-exclusive and direct-to-consumer formulations. Label review also understates exposure: prior chemical analysis by Helm and colleagues detected methylparaben in 72 percent and diethyl phthalate in 78 percent of hair products used by Black women, against label-declared prevalences here of 9.7 percent and none. Even within those constraints, the message is clear. Conditioners formulated for textured hair frequently contain potential sensitizers, do not always deliver the benefits their categories promise, and remain priced and distributed in ways that disproportionately burden the very communities they are designed to serve. Greater transparency in cosmetic ingredient disclosure, the authors conclude, is essential to equitable, evidence-based hair care.

Subject of Research: Formulation chemistry, allergen content, and retail accessibility of hair conditioners marketed for textured hair

Article Title: Formulation characteristics, safety, and accessibility of conditioners for textured hair

Article References: Bourne, A., Palmer, V., & McMichael, A. (2026). Formulation characteristics, safety, and accessibility of conditioners for textured hair. Archives of Dermatological Research, 318(1), Article 463. https://doi.org/10.1007/s00403-026-04949-1

Image Credits: AI Generated

DOI: 10.1007/s00403-026-04949-1

Keywords: textured hair, hair conditioners, contact allergens, cosmetic formulation, fragrance allergens, methylisothiazolinone, stearamidopropyl dimethylamine, hydrolyzed proteins, silicones, health disparities, pricing bias, dermatology