These Dyes Are Hurting Us, and they are in everything.  This page below is a good place to reference if your curious about what foods contain these  synthetic compounds.  Red #40 is not good for me.  I have been allergic since I was a kid.
This is the chemistry of red 40

I understand making food look pretty with dyes, but why are they putting it in prescribed drugs?
http://www.red40.com/pages/drugs/prescribed.html

Red Dye #40 in your diet  
 

Red Dye #40 is found in almost all categories of food. In nature, red is a very appealing food color; many fruits are colored red to indicate ripeness. As animals, we respond to those visual cues in our food and the food industry recognizes that fact.

As you'd expect, any food that has more to do with a laboratory than it does with the blue sky is likely to have been engineered for taste, longevity and appeal.

Most convenience foods have been carefully created for ease of manufacture, packaging, transport and shelf life. They are, in essense, "designed" much like a blender or a television set. In each case there are hundreds of factors to consider from the cost of raw components to the intended use of the product. The look of the product, whether it's a blender or a new soft drink, is an important feature because it must appeal to the consumer. For many foods that means a reddish hue, and one of the most cost effective and stable ways to achieve that color is with Red40.