How to Read SDS Section 3 for Ingredient Composition

Pull up any safety data sheet you have on file right now and skip straight to Section 3. That is the composition section, and it is where almost everything you need for a cosmetic filing actually lives, buried in a document most people only open when something spills.

A safety data sheet has 16 sections total, and Section 3 specifically lists composition. Sections 1 and 2 tell you what the product is and its hazards in general terms. Section 3 is where the actual ingredient identities, CAS numbers, and concentration information show up. If you are trying to figure out what is really in a supplier blend, this is the section worth reading slowly.

What a real Section 3 entry looks like

Here is a simplified example of how a Section 3 table typically presents a multi-component blend:

Chemical name	CAS number	Concentration (%)
Aqua	7732-18-5	60-70
Glycerin	56-81-5	15-25
Cetearyl Alcohol	8005-44-1	5-10
Fragrance component (proprietary)	Not disclosed	1-5

Notice a few things happening at once here. Water appears under its INCI name, Aqua, which is standard. Each component has a CAS number, except one, which is common when a supplier considers a specific fragrance or specialty component proprietary and withholds the CAS number even while including it in an SDS. Concentrations are given as ranges, not exact figures, which is typical because SDS documents are written to cover a formula's normal manufacturing variance without disclosing the exact recipe.

Why ranges instead of exact numbers

Suppliers give ranges in Section 3 for two reasons. First, most formulas have some natural batch to batch variance and a range covers that honestly. Second, an exact percentage would hand a competitor your recipe, so a range like "5 to 10%" protects the formulation while still giving you, the buyer, enough information to work with. When you carry this into your own cosmetic filing, you generally want to use the actual concentration you are working with in your formula, informed by the supplier's range, or the range itself if that is all you have confirmed.

What to do when a CAS number is missing

Some ingredients genuinely do not have one. Botanical extracts are the most common example, since a plant extract can be a complex mixture that does not correspond to a single registered substance. If Section 3 lists an extract with no CAS number, that is often expected rather than a documentation error. Match it by its INCI name instead, and do not assume the absence of a CAS number means the supplier is hiding something.

Where it is worth following up with the supplier is when a well-defined, single chemical entity is missing its CAS number and no explanation like "proprietary" or "trade secret" is given. That is more likely a documentation gap than a genuine case of an entity without a registry number.

Trade names never survive the trip to your filing

If your Section 3 lists a component only by a trade name, a blend's marketing name, or a supplier's internal code, that is not something you can file with directly. Trade names never appear on a filing. You need the INCI name behind it, which means either the SDS gives you enough to identify it, the supplier provides a separate ingredient statement or certificate of composition, or you contact the supplier directly and ask for the INCI breakdown.

This happens most often with fragrance blends and specialty complexes, where the SDS might just say "Proprietary Fragrance Blend, CAS Not Established" and expect you to request the fuller allergen and component declaration separately. Do not treat the SDS as your only source here. It is a starting point, not always the complete ingredient picture, especially for fragrance.

A reading checklist for Section 3

1. Confirm every listed component has either an INCI name or enough identifying information to map to one.
2. Note which CAS numbers are present and flag any missing ones for follow-up, unless the ingredient is a botanical extract where no CAS is expected.
3. Record concentration ranges as given, and confirm with the supplier which end of the range, or what specific value, applies to the batch you are actually using.
4. If the blend contains sub-components, remember that the percentage shown is the component's share within the blend, not its final concentration in your finished product, so you still need to multiply by your use level of the blend.
5. Flag anything marked proprietary or trade name only and request a fuller ingredient statement before you finalize your filing.

Reading a stack of SDS documents this carefully for every raw material in a formula is genuinely tedious work, and it is easy to miss a missing CAS number or misread a range under deadline pressure. Cosmetic Comply takes your ingredient list and supplier documentation and does this mapping for you, matching each component to its INCI name and CAS number and expanding blends into their real concentrations, so the composition data behind your filing is built the same careful way every time rather than depending on how closely you read Section 3 at 11pm before a deadline.