Q: What does Active vs Other ingredients mean? i.e. this is the ingredient list for Diorskin Nude Foundation, what does it mean if there's "alcohol" in the Other Ingredients section?
Active Ingredients: Titanium Dioxide 3.16% & Octinoxate 3%
Other Ingredients: Water, Methyl Trimethicone, Alcohol, Phenyl Trimethicone, Butylene Glycol, Cetyl PEG/PPG-10/1 Dimethicone, Silica, Acrylates/Dimethicone Copolymer, Acrylates Copolymer, Butylene Glycol Dicaprylate/Dicaprate, Phenoxyethanol, Stearic Acid, Sorbitan Sesquioleate, Alumina, Sodium Myristoyl Glutamate, Dimethicone, Ascorbyl Glucoside, Hydroxyethycellulose, Lecithin, Tocopheryl Acetate, Synthetic Fluorphlogopite, Parfum (Fragrance), Sericin, Linalool, Magnesium Aspartate, Zinc Gluconate, Methylparaben, Limonene, Butylphenyl Methylpropional, BHT, Rhodochrosite Extract, Dimethicone/Methicone Copolymer, Hydrolyzed Linseed Extract, Citronellol, Sorbic Acid, Butylparaben, Ethylparaben, Copper Gluconate, Isobutylparaben, Propylparaben.
+/-: Mica, CI 77002 (Aluminum Hydroxide), 77491/77492/77499 (Iron Oxides), CI 77891 (Titanium Dioxide).
A: "Active" ingredients are ingredients regulated as OTC drugs. Sunscreens fall into this category, so any product with an SPF rating must list its sunscreen ingredients as actives, and show instructions for use. Many (most) color cosmetics contain titanium dioxide, but if the product does not have an SPF rating, it will be listed with the rest of the ingredients instead.
In addition to my answer above, you may notice the "+/-" section at the bottom of the list. This is something you'll see in various forms in color cosmetic formulations, because of shade variations and other formulary variations between different versions of the same product. As you can see, titanium dioxide is also listed as a pigment ingredient there.
As an aside, I don't recommend that foundation--quite a lot of alcohol and other irritants! I know it's a high-end favorite, but it's definitely not something I'd suggest using on a regular basis.