Lettuce and other leafy vegetables are highly susceptible to bacterial contamination, particularly E. coli, Salmonella, and Listeria. With improper handling, lettuce can be a source of food poisoning (with diarrhea as the most common symptom), especially when eaten raw. To minimize the risk of foodborne disease, always wash lettuces (and other vegetables) before eating. Next to that, avoid buying and eating lettuces that look spoiled and mushy.