If you are trying to find a cleaner bar soap, reading the ingredient list is the right place to start. The challenge is that most soap labels are printed in small type, use INCI chemical names that are not immediately recognizable, and run twenty or more entries long.
Here is a plain-English guide to the common soap ingredients worth knowing — what each one is, why it is used, and why you might prefer to avoid it.
Sodium Lauryl Sulfate (SLS) and Sodium Laureth Sulfate (SLES)
What it is: Synthetic detergent surfactants derived from coconut or palm oil through an industrial process. They are the primary cleansing agents in most commercial bar soap and body wash.
Why it is used: Highly effective at removing oil and producing lather. Cheap to manufacture at scale.
Why to consider avoiding it: SLS and SLES are more aggressive than the fatty acid salts produced by saponification in natural soap. They disrupt the skin's moisture barrier, strip natural oils, and are documented irritants for people with sensitive, eczema-prone, or dry skin. If the ingredient list on your current soap starts with sodium lauryl sulfate, the product is a synthetic detergent bar, not genuine soap.
Fragrance / Parfum
What it is: A proprietary blend of aromatic chemicals listed under the single word "fragrance" or "parfum." The individual components are not required to be disclosed.
Why it is used: Differentiates products on the shelf. Masks the smell of synthetic ingredients in the base formula.
Why to consider avoiding it: Synthetic fragrance is the most consistently identified cause of contact allergic reactions in personal care products. It is the first ingredient to eliminate for anyone with sensitive, reactive, or eczema-prone skin. The fragrance label tells you nothing about what is actually in the blend.
Parabens (Methylparaben, Propylparaben, Butylparaben, Ethylparaben)
What it is: Chemical preservatives used to prevent microbial growth in water-containing products.
Why it is used: Effective, inexpensive, and stable over a long shelf life.
Why to consider avoiding it: Parabens are documented contact sensitizers and are among the more commonly avoided ingredients by people with skin sensitivities. They are also the subject of ongoing research regarding endocrine activity. Properly formulated small-batch soap does not require parabens to remain stable.
PEG Compounds (PEG-6, PEG-40, PEG-120, etc.)
What it is: Polyethylene glycols — synthetic compounds used as surfactants, emulsifiers, penetration enhancers, or thickeners.
Why it is used: Multiple functions depending on the specific PEG and its molecular weight. Inexpensive and stable.
Why to consider avoiding it: Not inherently dangerous, but entirely synthetic and unnecessary in genuine natural soap. Their presence on a label indicates the product is a synthetic formulation, not saponified oil.
Artificial Color (FD&C Dyes, Colorants)
What it is: Synthetic dyes typically listed as FD&C Blue 1, FD&C Red 40, or similar.
Why it is used: Purely aesthetic. Commercial soap is artificially colored to look appealing on a shelf.
Why to consider avoiding it: No skin benefit. Common sensitizer. A natural soap bar made from quality oils does not need color — the oils provide a natural, neutral appearance.
BHT and BHA (Butylated Hydroxytoluene / Butylated Hydroxyanisole)
What it is: Synthetic antioxidant preservatives that prevent oxidation and extend shelf life.
Why it is used: Effective at preventing rancidity in commercial products stored for long periods.
Why to consider avoiding it: Synthetic preservatives that serve no skin function. Small-batch soap formulated without free water and properly cured does not require them.
What a Clean Label Looks Like
A clean bar soap has a short ingredient list made up of saponified oils. The entire ingredient list for the No. 3 Bar is: Saponified Avocado Oil, Saponified Coconut Oil, Saponified Olive Oil. Three entries. Each one identifiable. Nothing else.
That is the benchmark. See the No. 3 Bar.