FDA Approved? What 21 CFR 175.300 Actually Says About Driers and Photoinitiators

Last reviewed: 18 September 2026. Read against the current text of 21 CFR 175.300. Regulation text is quoted from the CFR; the interpretation is ours.

Every few weeks someone asks whether a photoinitiator we supply is FDA approved. The question usually arrives with a competitor's web page attached, and the honest answer is that the phrase does not mean what it appears to mean. This article explains what the US rules actually say for the two product families involved, because the answer is dramatically different for each and almost nobody states it plainly.

First, a vocabulary problem

"FDA approved" is not a category that exists for food-contact substances. The FDA does not approve raw materials in the way it approves a drug. What exists is a set of routes by which a substance becomes lawful for a specific food-contact use.

A substance may be listed in a regulation, such as a section of 21 CFR Part 175. It may be the subject of a Food Contact Notification, which is submitted by a specific manufacturer, covers a specific use, and belongs to them rather than to the substance. It may fall under the Threshold of Regulation exemption at 21 CFR 170.39, which turns on dietary concentration rather than on identity.

Each of those routes is narrower than "approved". A substance with an FCN is lawful for the use described in that notification and for the company that filed it. It is not lawful generally. A competitor claiming that a raw material is "FDA approved" because an FCN exists somewhere is describing someone else's permission.

Chinese supplier websites are a common source of this error, and it is worth saying directly: we do not make that claim, and you should be suspicious of any supplier who does.

The driers: a genuine, quotable approval

Now the good news, and it is considerably better than the photoinitiator position. Driers used in resinous and polymeric coatings are expressly listed in the United States.

21 CFR 175.300(b)(3)(xxii) provides for "Driers made by reaction of a metal from paragraph (b)(3)(xxii)(a) of this section with acid, to form the salt listed in paragraph (b)(3)(xxii)(b)". The two lists are short enough to reproduce in full.

Permitted metals	Permitted salts
Aluminum Calcium Cerium Cobalt Iron Lithium Magnesium Manganese Zinc Zirconium	Caprate Caprylate Isodecanoate Linoleate Naphthenate Neodecanoate Octoate (2-ethylhexoate) Oleate Palmitate Resinate Ricinoleate Soyate Stearate Tallate

Any combination of a listed metal with a listed salt falls within the provision. Read that against our range:

Product	Metal	Salt	Within 175.300(b)(3)(xxii)?
Cobalt Octoate	Cobalt	Octoate	Yes
Cobalt Naphthenate	Cobalt	Naphthenate	Yes
Manganese Octoate	Manganese	Octoate	Yes
Manganese Naphthenate	Manganese	Naphthenate	Yes
Zirconium Octoate	Zirconium	Octoate	Yes
Cerium Octoate	Cerium	Octoate	Yes
Lead Naphthenate	Lead	Naphthenate	No. Lead is not on the metal list.

Two things follow, and the second is worth pausing on.

The first is that six of the seven driers we supply fall within an express federal listing. That is a real, checkable statement, and it is a far stronger position than any amount of "FDA approved" language.

The second is that lead is not on the list. Lead naphthenate is a traditional through-drier with a long history of use, and it appears in none of the ten permitted metals. If a supplier tells you their lead drier is 175.300 compliant, ask them to point at the metal list. It is not there, and that is before we get to the European position, which is stricter still.

The photoinitiators: nothing is listed, and that is the accurate answer

Now the part that competitors avoid, and the reason this article exists.

We searched the full text of 21 CFR 175.300. The word "photoinitiator" does not appear in it. Nor does any CAS number from our photoinitiator range, or from the ranges our competitors sell.

The reason is structural rather than an oversight. Section 175.300 governs resinous and polymeric coatings and lists the substances that may be used to build them: drying oils, rosins, phenolic and epoxy and polyester resins, catalysts, cross-linking agents. Photoinitiators are not among them, because when the section was written UV curing was not the industrial process it is now.

So the accurate statement for the photoinitiator range is this: none of the photoinitiators we supply is a listed indirect food additive under 21 CFR 175.300. That is true of our range and it is true of our competitors' ranges, whether or not their websites say otherwise.

There are two narrow exceptions worth knowing, and both are narrower than they sound.

Irgacure 2959 chemistry, which is our NPI-501, is listed in 21 CFR 175.105 and 175.125 for use as a photoinitiator at a level not exceeding 5 percent by weight of the adhesive. It is a genuine listing and it is use-specific. It is not a general food-contact approval, and it does not travel to inks or coatings.

1173 has Food Contact Notification coverage, in FCN 41 and FCN 369, both filed by Evonik for cured silicone acrylate. FCNs are proprietary and use-specific. Their existence tells you that one company obtained clearance for one application. It does not make 1173 generally usable, and a supplier who cites an FCN as if it were a public listing is misreading how FCNs work.

What about the "no migration" route?

The United States has no specific migration limit system for this category in the way the EU does, and it has no formal "low migration" classification.

The nearest equivalent is the Threshold of Regulation exemption at 21 CFR 170.39, which applies where the substance's dietary concentration is at or below 0.5 parts per billion, corresponding to roughly 1.5 micrograms per person per day. That is a demanding threshold, and reaching it depends on the finished article rather than on the raw material.

You will see the phrase "no-migration exemption" used in this market. It is industry shorthand rather than a citable FDA category, and we would not build a regulatory argument on it.

Related: polyisobutylene has a molecular weight gate

One further US provision matters for our range, because it is commonly misquoted.

21 CFR 177.1420 covers polyisobutylene, and it sets a minimum molecular weight: 750,000 Flory for the homopolymer, or 300,000 for the isobutylene-isoprene copolymer with no more than 3 mol% isoprene. Separately, 177.1420(c) expressly does not apply to PIB used in food-packaging adhesives complying with 175.105.

That gate matters because low molecular weight PIB, in the 500 to 3,000 range, does not meet it. Many suppliers quote 177.1420 generically for any polyisobutylene they sell. Our food grade PIB comes in both high-activity and low-activity grades, and the molecular weight of the grade you buy determines whether 177.1420 applies. Ask us which grade you are being quoted against, and we will tell you which route applies rather than hand you a citation that may not fit.

What to ask a supplier

Four questions, and the answers are checkable.

Which provision, by section number? "175.300(b)(3)(xxii)" is a checkable answer. "FDA approved" is not.

Is it a listing, an FCN or a Threshold of Regulation exemption? These are different things with different scopes, and a supplier who cannot tell them apart does not know your regulatory position.

If it is an FCN, whose is it, and what use does it cover? An FCN is not transferable permission.

For a mixture or an article, what is the migration data on a construction like mine? A raw material listing does not answer this, and in the US the relevant test is the extraction protocol in 175.300(e), run against simulants matched to your food type and conditions of use.

Our position

For the six non-lead driers in our range, we will tell you that they fall within an express listing at 21 CFR 175.300(b)(3)(xxii), and we will show you the list so you can confirm it. For our photoinitiators, we will tell you that they are not listed, because that is the accurate answer, and then we will talk about what your application actually needs.

If a competitor is telling you their photoinitiator is FDA approved, one of you is about to learn something. Ask which section.