Leave-In Molecular Repair Hair Mask

The base most products are built on. It carries the other ingredients and has no safety concern.

A fast-evaporating solvent used to carry actives and give toners a light, "clean" feel; at the concentrations used in classic astringents it can be genuinely drying or irritating with repeated use, especially on dry or compromised skin, though it is not inherently toxic and is a normal, well-studied cosmetic ingredient.

A small humectant and solvent molecule that helps other ingredients dissolve and helps skin hold water. It is one of the most studied cosmetic ingredients and is considered safe at the concentrations used in personal care products.

A blend of cetyl and stearyl fatty alcohols used to thicken lotions and soften skin. It is chemically unrelated to drying alcohols like ethanol, and the CIR expert panel has found fatty alcohols safe as used in cosmetics.

A light, fast-absorbing emollient that improves spreadability and gives a silky finish without grease. It is well tolerated and graded low concern in published assessments.

A quaternary ammonium conditioning agent that coats hair with a positive charge to smooth the cuticle, cut static, and ease detangling; it is one of the most common conditioning ingredients in rinse-off conditioners. CIR reviewed it as part of the trimonium family and found it safe as used, including in leave-on formulas at typical concentrations.

A widely used emulsifier and solubilizer that has been in cosmetics and pharmaceuticals for decades. The CIR has assessed it as safe with no known concerns at typical cosmetic concentrations. As with any surfactant, some people with very sensitive skin may experience mild irritation.

A protein fragment that draws water into the hair shaft and is used to strengthen and add body. People with wheat sensitivity or protein allergies should patch-test first, as protein hydrolysates can trigger reactions in those with known sensitivities.

An antioxidant that helps protect a formula and condition skin. Well tolerated.

A widely used preservative, safe at the legal limit of 1% or less. Often the "paraben-free" replacement.

A widely used, gentle preservative also common in food. It is generally well tolerated, though it can occasionally cause mild, transient irritation in people with already-compromised or very reactive skin.

Used in tiny amounts to set a product to skin-friendly pH. No concern at those levels.

An undisclosed scent blend that can contain dozens of components. The single most common cause of cosmetic contact allergy, and the blend is not itemized, so you cannot see what is in it.

A floral, rose-like fragrance compound found in many essential oils. It is one of the 26 EU-designated fragrance allergens, meaning a documented minority of people can develop contact sensitization, so brands must disclose it above set thresholds.

A floral fragrance component and one of the EU-labelled fragrance allergens. Usually fine, worth watching if you react to scented products.

A jasmine-like fragrance compound frequently used in soaps and lotions. It is one of the 26 EU-designated fragrance allergens, though studies suggest its sensitization potency is comparatively low relative to other listed allergens.

A common preservative and fragrance/solvent ingredient found naturally in many essential oils. It is well tolerated by most people at the levels used in cosmetics, but it is one of the 26 EU-designated fragrance allergens and can trigger reactions in people with an existing sensitivity.