Tartrazine is a yellow food colouring, so can be present in any yellow or orange foods. It is always listed in the additives, though. The problem is that some studies have linked it to hyperactivity, particularly in young boys. Other people have varied intolerances to it. Regardless of the truth of this if you are worried avoid it...dont eat anything with artificial colours in it.
Tartrazine is a dye made from coal tar and can still be found in some cakes, biscuits, soft drinks as well as fish batter and chips. It's also fed to chickens to make egg yolks very yellow.
Research has linked tartrazine to asthma, some rashes, hyperactivity and migraines.
You'll find it on labels as E102 .