Food dyes are added to many foods to change their color. Consider Fruit Loops: Each piece of cereal is another shade. A number of people have adverse reactions to the coloring added to foods. In some cases, the medical community refers to these adverse reactions as allergies; in others, they're considered food intolerance. For example, a study done by the University of Michigan found that the reddish coloring called cochineal extract or carmine dye -- which is made from cochineal bugs found in South America and the Canary Islands -- posed a life-threatening allergic risk of anaphylactic shock in some people. The risk is rare, as it is with most allergies. This coloring is commonly added to food, drinks and cosmetics.
In other cases, the sensitivity to colorants like yellow dye number 5 is considered food intolerance, although the reactions associated with the intolerance are very close to those associated with food allergies. People with intolerance for yellow dye number 5 might find themselves breaking out in hives, which is typically a response caused by the histamine that an allergic response creates. Other food dyes that are known to cause allergic-like responses are blue 1, red 40 and yellow 6, according to a study by the Center for Science in the Public Interest.
The difference between a food allergy and food intolerance is that a food allergy is an immune system response to a protein that your body misidentifies as dangerous, while food intolerance is a digestive system response to foods that it can't break down for one reason or another. In a food allergy, your immune system releases a team of chemicals to fight off an allergen, and the battle is what you identify as allergic symptoms. Allergies can be triggered by even minute amounts of a substance, whereas food intolerance is often dose-related.