Taylor
Are you sure it is the lettuce you are getting the reaction to. I bet in each of the incidents the kitchen prepared the salad with a product that retained the color of the salad. Not wanting to bash any name brand-but an item along the lines of "Fruit Fresh" or monsodium glutamate. I get an intestanal reaction when I eat salad prepared with a "freshness retainer" Check it out the next time you are dining out!