Why Eat Real Blueberries When You Can Have Artificial Blueberry Bits with Red 40 and Blue 2?

To further complicate matters, a blue drug isn’t always made with blue dye. American Pharmacists Association media liaison Norman Tomaka (BS, MS in Pharmacy) says, “Just because a tablet’s purple, or just because a tablet’s green, doesn’t mean that’s the dye that’s used in it.” For example, Dulcolax, a red laxative, contains FD&C Yellow #10 aluminum lake.

Coloring That Does Double-Duty as a Binding Agent

Then there are coloring agents like cobalt that also double as binding agents, a type of inactive ingredient that manufacturers use to physically “bind,” or hold, a medicine together. Cobalt allergies, according to Dr. Purvi Parikh, an immunologist with Allergy and Asthma Associates of Murray Hill in New York, are common. Cobalt is frequently found in vitamin B12.

While all this is interesting, here’s why it matters: You may be allergic to a color additive, and that allergy could be keeping you from taking medicine you truly need.

Tomaka says approximately 40% of the population thinks they’re allergic to penicillin class drugs, but less than 10% actually are.

Another natural blue dye is made from watermelons and a fruit known as “huito.” It also is close to the color of Blue 2.