Re: What is the chemical injected into veins to make them glow?

Jesse-There is no actual chemical that makes veins "glow".  What the 
chemical or substance is-is called radiopaque agents which are used in 
x-ray studies to visualize various organs or blood vessels in the body.  
Radiopaque or contrast agents are iodine based, and the degree of density 
of the material is believe it or not based on the percentage of iodine in 
the chemical-this is because of iodine's relatively high molecular weight. 
    As with any medicine there can be some side-effects or allergic 
reactions.  If a person is going to have an x-ray dye study with one of 
these contrast agents, we are very careful if they have a history of 
allergy to iodine.  Also, we want them to be well hydrated and to know that 
their kidneys are working well(usually, we need a blood test to check 
kidney function prior to doing one of these studies).  There can be mild 
side effects like skin rashes, upset stomach, nausea, vomitting, dizziness, 
and heartburn (these are also possible with any medicine).  And 
occasionally, some can have a very severe side effect with problems with 
breathing etc.  The dye studies are used frequently and are very valuable 
in X-rays, CT, MRI for almost any organ or blood vessel system .