Early on in our search for JT safe foods I was surprised by how many products contained ingredients that were unexpected. I was really surprised to find that some chicken stock/broth contained milk. Since then we have found several chicken broths (or stocks) that are safe for JT. Recently, though, I found Kitchen Basics chicken stock and was really pleasantly surprised. Not only does this stock have a really rich and delicious flavor they actually test their stock for trace amounts of allergens.
From their box:
We reduce the risk of allergen reactions by specifying that our ingredients must not contain milk, eggs, peanuts, gluten, soy, tree nuts, fish, shellfish or corn. Each production run is tested for the absence of these allergens to 5ppm.