Miracle Leave-In Product

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

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 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 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 protein fragment derived from animal keratin that helps hair retain moisture and improves strength and shine. It is well tolerated across hair types and does not carry the allergen risk of plant-derived hydrolyzed proteins.

A lightweight, volatile silicone that gives serums and primers their silky slip and quick-evaporating finish. Human safety data are reassuring; the EU restriction on this ingredient in rinse-off products is about environmental persistence in waterways, not skin safety.

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.

Green tea extract is a well-studied topical antioxidant with a long history of use in serums and moisturizers, generally well tolerated at cosmetic concentrations. Panel safety reviews of Camellia sinensis-derived ingredients have not identified meaningful topical hazard.

A plant-derived water or extract used mainly as a soothing humectant filler. Evidence for dramatic skin benefits beyond mild hydration and soothing is limited, but it is well tolerated by most people.

A lightweight humectant and solvent similar in role to propylene glycol, used to carry actives and give lotions a lighter feel. CIR has reviewed it and considers it safe as used in cosmetics.

A soothing humectant that helps skin and hair look conditioned. Very well tolerated.

A preservative that works by slowly releasing small amounts of formaldehyde to keep microbes from growing in the product. It is a well-documented contact allergen for a subset of users, which is why formaldehyde releasers are worth knowing about even though most people tolerate them fine.

Hydroxycitronellal is a lily-of-the-valley scented fragrance ingredient on the EU allergen disclosure list. It has well-documented sensitizing potential in patch-test studies, so it is worth checking the label if you have known fragrance sensitivities.

Benzyl salicylate is a fragrance fixative that also absorbs some UV light. It is on the EU allergen disclosure list, but the evidence suggests it sensitizes fewer people than most other listed fragrance allergens.

Butylphenyl methylpropional, widely sold under the trade name Lilial, was banned from cosmetics in the EU starting March 2022 after being classified as toxic to reproduction based on animal studies. Products made and sold in the EU after that date should no longer contain it.

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

A rose-scented fragrance ingredient found naturally in geranium and rose oil. It is one of the 26 fragrance allergens the EU requires to be labeled by name because a minority of people develop skin sensitization to it, though most users tolerate it without issue.

A citrus-scented fragrance component. Fine for most, but it oxidizes over time into a known contact allergen, so it must be labelled in the EU.

A preservative that keeps products free of mold and bacteria. Reviewed repeatedly and considered safe at the low levels used.

A member of the paraben family used to prevent microbial growth in cosmetics. Like methylparaben, it has been reviewed extensively and found safe at the concentrations used in leave-on and rinse-off products.

Methylchloroisothiazolinone is typically used together with methylisothiazolinone in a 3:1 mix and is a well-documented skin sensitizer at higher rates than most preservatives. EU rules now restrict this combination to rinse-off products only, at a low maximum concentration.

A preservative that caused a wave of contact allergy in the 2010s. The EU banned it from leave-on products and tightly limits it in rinse-off ones. A genuine concern, not a myth.