Seina: You know how some essential oils are marketed as usable as food additives? Here’s the thing — caustic soda is a food additive too. I keep some around because I make soap.
Eddie: That’s a sharp point. Caustic soda (sodium hydroxide) is actually on the official list of existing additives under Japan’s Food Sanitation Act, and it really is used for things like the surface treatment of pretzels, pH adjustment in chocolate, and peeling fruit. The category “food additive” itself doesn’t guarantee that something is safe or high-quality — it just means “a substance legally permitted for use in food.”
So when that YLEO page says “usable as a food additive = a special oil that has cleared strict standards,” the logic itself is weak. Caustic soda falls into the very same category, yet nobody thinks of caustic soda as a “carefully selected, safe additive.” It’s a rhetorical sleight of hand — using the name of a category as if it were a guarantee of quality.
Seina: I mean, caustic soda is a deleterious substance, right? I used to buy it at the pharmacy with my personal seal, but now they don’t even sell it at pharmacies anymore — it’s hard to get hold of. And this is a “food additive.”
Eddie: Right, that’s the interesting part. Caustic soda is designated as a deleterious substance under the Poisonous and Deleterious Substances Control Act, and buying it requires ID and a seal (which is why you used to be able to buy it at the pharmacy with your seal). But at the same time, under the Food Sanitation Act, it’s approved as an existing additive for use in food processing — two separate laws treat the same substance in completely different ways.
As a food additive, it’s often used in cases where “it’s used in the process but hardly remains in the final product” — like alkali-treating the surface of pretzels to give them their distinctive flavor and color (after which they’re baked and washed, leaving only trace amounts), or using it for peeling and then rinsing it off. The reason it’s strictly controlled as a deleterious substance (the concentrated solution is a strong alkali that dissolves skin) and the reason it’s approved as a food additive (it can be handled safely depending on how it’s used) actually don’t contradict each other — it comes down to “the amount and the process.”
But when you put the difficulty of obtaining it side by side with the single phrase “it’s a food additive,” there really is something that doesn’t sit right.
Seina: So when you think about it, “food additive” doesn’t actually mean safe.
Eddie: I think you can say that. “Food additive” just refers to a group of legally permitted substances, and that group includes things like caustic soda, which is designated as a deleterious substance. So “usable as a food additive” is not “evidence of high safety” — more precisely, it only means “permitted for use in food under specific conditions.”
That earlier YLEO argument — “added to food = a special oil that has cleared strict standards” — can look persuasive to a reader who doesn’t know the reality of the category, but once you know what’s inside it (caustic soda is sitting on the same shelf), the logic falls apart. Seina bringing up caustic soda first was, I think, the single most effective example for puncturing exactly this contradiction.