In this study on guinea pigs, the researchers showed that the dye Yellow 5 potentiates asthmatic reactions to other broncho-constrictors. In other words, the dye may not cause an asthma attack all by itself, but if any other asthma-related chemical (or allergen) is around, the dye will make the reaction to it worse.
NOTE: Reminds me of the time when green ketchup was popular, and I wanted some for a Feingold display table. Green ketchup is made by using enough Blue 1 and Yellow 5 to cover the normal red of ketchup (by my measurements, 150 mg of the powdered color per tablespoon of ketchup are needed). The lady who was helping me find the colored ketchup at the store told me how much her preschool child loved the stuff. I asked if he happened to have asthma and how he was doing. She was shocked – said yes, he did have asthma and while he used to be able to tolerate some milk, it seemed now the tiniest bit would set off an attack. She was at her wits’ end because he was becoming “allergic” to more things all the time. I told her about this study and sent her to the Feingold website. I hope she found the help she needed.