What Counts as Soap Under FDA's Rules

What the rule says

The definition sits in 21 CFR 701.20, and it opens by admitting a gap. The Federal Food, Drug, and Cosmetic Act “specifically excludes soap” from its definition of a cosmetic, but “the term soap is nowhere defined in the act.” So FDA set out how it reads the word. A product is soap only if “the bulk of the nonvolatile matter in the product consists of an alkali salt of fatty acids and the detergent properties of the article are due to the alkali-fatty acid compounds,” and if “the product is labeled, sold, and represented only as soap.”

The next paragraph says what everything else is. Products “intended for cleansing the human body and which are not ‘soap’” under that definition “are ‘cosmetics,’ and accordingly they are subject to the requirements of the act.” The rule’s own example is a bar: such a product in bar form has to carry a label stating the weight of the bar in pounds and ounces.

What that means for the bar in your shower

FDA’s Frequently Asked Questions on Soap restates the rule as three conditions and says “all three conditions must be met.”

What it’s made of. The product “must be composed mainly of the ‘alkali salts of fatty acids,’ that is, the material you get when you combine fats or oils with an alkali, such as lye.”

What does the cleaning. Those salts “must be the only material that results in the product’s cleaning action. If the product contains synthetic detergents, it’s a cosmetic, not a soap.”

How it’s sold. “It must be labeled and marketed only for use as soap. If it is intended for purposes such as moisturizing the skin, making the user smell nice, or deodorizing the user’s body, it’s a cosmetic.”

Then the sentence that matters for a shopper, which the FAQ repeats under two of the three conditions: “You can still use the word ‘soap’ on the label.” The regulatory category and the marketing word are separate things, and the wrapper only gives you the second.

Why so few bars qualify

FDA describes the market plainly. “Today there are very few true soaps on the market. Most body cleansers, both liquid and solid, are synthetic detergent products.” It explains why they sell: “detergent cleansers are popular because they make suds easily in water and don’t form gummy deposits.” And it closes the loop: “Many of these detergent products are marketed as ‘soap’ but are not true soap according to the regulatory definition of the word.”

The ingredient list is where the two kinds part. A true soap’s list is dominated by the salts the rule names, which appear under names like sodium tallowate, sodium palmate, or sodium cocoate, or as the oils and lye they were made from. A detergent bar’s list leads with a synthetic surfactant instead. The rule doesn’t ask you to read the list, but it is the only place on the package where the distinction shows.

Who regulates which

The category decides the regulator. FDA’s FAQ states that a product meeting its definition of soap “is regulated by the Consumer Product Safety Commission (CPSC), not by FDA.” A cosmetic is FDA’s, and “neither the product nor its ingredients need approval by FDA before they go on the market, except for any color additives it contains.” A drug is FDA’s too, and has to follow a monograph or carry an approval. A product “intended to treat or prevent disease, such as by killing germs, or treating skin conditions, such as acne or eczema,” is a drug, and What “Antibacterial” Hand Soap Actually Requires covers the rule that applies to the germ-killing claim specifically.

One more line from the FAQ belongs here. “The laws and regulations that FDA enforces do not have definitions for ‘natural’ or ‘organic.’” A bar that says either is making a claim these rules don’t define.

Runlow does not yet carry product records for bar soap, so this post names no brand. When it does, each bar’s ingredient list will render from the record, the way every product fact on this site does, and the list is what shows which side of this line a bar sits on.

Where this comes from

Every statement above is quoted from 21 CFR 701.20 or from FDA’s own soap FAQ, both linked in the text. Runlow has not tested any soap and makes no claim about any brand. Nothing here is a statement about what any bar does to skin; the rule sorts products by what they are made of and how they are sold, and this post goes no further than that.