As for home-cooked meals, while it is easy to measure the amount of salt called for in a recipe, it gets more complicated if the dish calls for soy sauce, or some other ingredient which contains salt.
Since 2006, food manufacturers have been required to clearly label products that contain any of the most common allergens -- milk, eggs, fish, shellfish, peanuts, tree nuts, wheat and soy -- but some allergy experts say the labels should be more explicit.