Blue 2

Blue 2 is FD&C Blue No. 2, a synthetic dye. FDA lists it among color additives that must be batch certified before use in food, and each batch must meet FDA purity specifications. Long-term research on Blue 2 in cats is close to nonexistent, and it has no nutritional purpose. For a cat with a medical condition, your veterinarian is the best person to ask about its food.

Source: ecfr.gov

Blue 2 is there to color kibble. Mixed with red or yellow dyes, it helps make pieces look like meat or vegetables that shoppers recognize. Cats rely far more on smell and taste than on color when they eat, so the dye is aimed at people. It adds no nutrients to the food.

FDA's listing describes FD&C Blue No. 2 by its chemistry rather than by a common name: it is principally the disodium salt of a sulfonated indigo compound. It is a different compound from Blue 1, which has its own listing. On a US cat food label you will usually see it written as Blue 2 or as Blue 2 Lake.

Source: ecfr.gov

Yes, Blue 2 is on FDA's list of color additives for food, in the group that requires batch certification. That means FDA tests each batch for purity before it can be used. Approval sets the conditions for use. It does not mean the dye adds anything for a cat, and FDA said in 2026 it would use enforcement discretion for certain claims on animal foods made without certified colors.

Source: fda.gov

Pettings gives Blue 2 0 out of 5 and lists it as an artificial color. It appears on 15 of the 149 dry cat foods we list. Synthetic dyes get our lowest score because they are added for the buyer's eye and add nothing for the cat. Each food's page shows how it scores overall.