Why Certain Ingredients Get a Bad Rap — The Science Behind the Scare
There’s a lot of fear floating around the hair world: “no parabens,” “sulfate-free,” and “ammonia free.” As someone who cares about health and honest products, but also science, I want to cut through the noise. The reality is more nuanced: most ingredients are safe when used appropriately, while others deserve scrutiny based on formulation and exposure. Here’s a easy to understand guide on just a few of the top controversies, to what the science actually says.
Parabens — what they are and why people worry What they are: Parabens (methylparaben, propylparaben, etc.) are preservatives used to prevent microbial growth in cosmetics. They’ve been used for decades because they’re effective and inexpensive.
Why they were vilified: Parabens can mimic estrogen in lab tests, and traces have been detected in human tissue, which led to concerns about links to breast cancer and hormone disruption.
What the science says: The big experts (FDA, European Scientific Committee on Consumer Safety, Cosmetic Ingredient Review) have concluded that parabens used at approved concentrations in cosmetics are safe for consumers. The evidence linking parabens at real-world exposure levels to breast cancer or meaningful endocrine disruption is weak and inconsistent; many initial alarms came from in vitro or animal studies at extremely high doses that would be nearly impossible for most humans to be exposed to.
Furthermore, there have been issues with several products on the market needing to be recalled due to mold growth, most likely because of the lack of preservative use.
Even the word preservative often gets bad rap, but remember, even simple table salt (sodium chloride) is a great preservative. Salt however can be drying to hair, consider how your hair feels after a swim in the ocean, so just because something sounds safe doesn’t mean its great for your hair, just like not knowing the scientific term doesn’t make it bad for you either!
References:
U.S. Food & Drug Administration (FDA) summary: https://www.fda.gov/cosmetics/cosmetic-ingredients/parabens
Cosmetic Ingredient Review (CIR) safety assessment: https://www.cir-safety.org/ingredients
Sulfates (SLS, SLES) — cleansing power vs. irritation What they are: Sodium lauryl sulfate (SLS) and sodium laureth sulfate (SLES) are surfactants — they make lather and remove oils and dirt. Our scalps need to remain clean to support healthy hair growth, this is a whole other topic I’ll have to dive into separately though!
Why they were vilified: People equate “stripping” hair with damage. While SLS can irritate sensitive skin and remove natural oils, even in small amounts its an extremely effective cleanser, and is often replaced with even more stripping or drying ingredients when removed from formulations so its important to consider what your own personal needs are in regards to the amount of cleansing, dry skin? Sulfate free shampoo may be perfect, oily skin however? you may actually benefit from this ingredient.
References:
Cosmetic Ingredient Review (SLS/SLES assessments): https://www.cir-safety.org/
Review on surfactants and skin irritation: J Cosmet Dermatol. (example review) https://pubmed.ncbi.nlm.nih.gov/xxxxxxx/ (search “sodium lauryl sulfate skin irritation review”)
Ammonia — Why permanent haircolor uses it, and what the alternatives mean
What it is: Ammonia raises hair cuticle to allow color molecules to penetrate. It’s effective, inexpensive, and reliable in permanent and high-lift color formulations.
Why it was vilified: Ammonia has a strong odor and can be irritating to the scalp and respiratory system in poorly ventilated spaces. That smell and immediate discomfort led to a perception of it being “dangerous.”
What the science says: Ammonia is an effective alkalizing agent, and, when used in properly formulated professional products and with correct ventilation and application, it is safe. Alternatives (amine compounds like MEA or ethanolamine) can be milder in odor but often require different formulations and may act more slowly or not lift as effectively. Safety comes from correct formulation, trained application, and following product directions. Also, like most things, haircolor has come a long way in becoming healthier and more effective over the last couple decades, so formulas have already changed pretty significantly from the old days.
References:
Cosmetic chemistry texts and product safety summaries (search “ammonia in hair color safety”)
Regulatory perspectives: EU cosmetic safety reviews (SCCS) and product ingredient listings
Putting it together — risk is always about dose, exposure, and context
Dose matters: Toxicology’s first rule is “the dose makes the poison.” Many alarming lab results use concentrations far above real-world cosmetic exposure. Anything can be toxic, even water, it just depends on the amount.
Formulation matters: An ingredient’s effect depends on what it’s mixed with and how it’s delivered. Preservatives, surfactants, and alkalizers behave differently in finished products than in isolation.
Application matters: Professional application, ventilation, and following manufacturer instructions reduce risk.
Individual sensitivity matters: Allergies and sensitivities exist. Patch testing, professional consultation, and product swaps (e.g., sulfate-free shampoo for dry curls) are sensible but not always necessary.
Practical guidance for clients
Don’t buy fear — buy results. Choose products based on hair type, scalp sensitivity, and the results you want.
If you have sensitive skin or a history of reactions, ask for patch testing or choose milder alternatives.
For permanent color or high-lift jobs, trust a professional to pick the right formula and use proper safety measures.
Check reputable sources (regulatory agencies, peer-reviewed reviews) rather than clickbaity headlines or unlicensed and often under-informed influencers.
Ingredients aren’t heroes or villains by name — context makes them useful or problematic. As a stylist, I care about safe, effective results, and I’ll always choose products and techniques that balance performance and client comfort.