Reading the SDS for a Cosmetic Preservative Blend

Preservative blends are where a lot of first-time filers get tripped up, because the trade name on the drum almost never tells you what's actually in it. Something sold as "Preservative XYZ" might be two, three, or even four active ingredients suspended in a carrier, and your notification needs every one of them listed by INCI name at its real concentration in your finished product. The SDS is where you go to untangle that.

Start with Section 3

Section 3 of a 16-section SDS is Composition/Information on Ingredients, and for a blend, this is the section that matters most. A typical entry might look something like this:

Component	CAS number	Concentration in blend
Phenoxyethanol	122-99-6	80-90%
Ethylhexylglycerin	70445-33-9	8-12%
Water (Aqua)	7732-18-5	Balance

Notice the ranges. Suppliers often give a band rather than an exact number, partly to protect their formulation and partly because blends have normal batch-to-batch variance. That's fine for the SDS, but you'll want to ask the supplier for a tighter number, or at least confirm which end of the range to use, when you're filling out your own notification.

The math you actually need to do

Say your formula calls for 1.0% of this preservative blend. You don't file "1.0% Preservative XYZ." You file the actual INCI-named components at their true concentration in your finished product, which means multiplying the blend's use level by each component's share of the blend.

Using the midpoint of the ranges above (85% and 10%):

• Phenoxyethanol: 1.0% x 0.85 = 0.85% in your finished product
• Ethylhexylglycerin: 1.0% x 0.10 = 0.10% in your finished product
• Water: negligible, already accounted for as part of your total water phase

This is the calculation that trips people up most often on a first filing. It's easy to see "1% of the blend" and assume that's the number that goes on the form, when really each component needs its own line at its own true percentage.

Why this matters beyond paperwork

Phenoxyethanol has a widely recognized usage ceiling in finished cosmetics, and different markets have their own restricted-ingredient lists that set limits ingredient by ingredient. If you're only tracking "1% of the blend" without breaking out the actual phenoxyethanol percentage, you have no way of knowing whether you're anywhere near a limit, especially if you're also using phenoxyethanol elsewhere in the same formula, say in a separate fragrance carrier or another blended additive. Concentrations from every source of the same ingredient need to be added together.

Watch for INCI name mismatches

Some SDS documents, especially from smaller or overseas suppliers, use chemical names or trade jargon in Section 3 rather than the standardized INCI name. "2-Phenoxyethanol" and "Phenoxyethanol" are the same thing, but if you copy the SDS wording verbatim onto a notification, you may end up with a name a reviewer doesn't recognize as matching the INCI dictionary. Always cross-check the CAS number against the INCI name, since the CAS number is the more reliable anchor when wording varies.

When the SDS doesn't give you enough

Sometimes a supplier's SDS lists a component only as "proprietary preservative blend" with no useful breakdown at all, especially if a formula is trade-secret protected. When that happens, you need to go back to the supplier directly and ask for a full composition breakdown for regulatory filing purposes. Reputable ingredient suppliers expect this request and usually have a standard document ready, sometimes called a regulatory statement or a full disclosure sheet, separate from the SDS itself.

Keep the paper trail

Once you've done this math for a blend, save it. If you ever tweak your formula, even slightly, having the blend's expanded components already calculated saves you from redoing the work from scratch. This is one of the areas where a tool built for this specific job earns its keep. Cosmetic Comply expands supplier blends into their component INCI names and CAS numbers automatically and carries the percentages through, so a blend like the one above doesn't have to be hand-calculated every time you touch the formula.