Not generally containing any milk products, mayo should be OK for the lactose intolerant... but might I suggest that taking tuna salad or egg salad sandwiches in a packed lunch might not be the best idea if you don't have access to good refrigeration..... (you said outside sales - so I'm guessing you travel around a lot?) The bloaty feeling could be mild food poisoning.

(btw yogurt and cheese is OK for many people who are lactose intolerant as it contains bacteria and/or enzymes that break down lactose for you. Milk allergy is different, if you have milk allergies you need to avoid milk completely as you are allergic to the proteins in milk. Lactose intolerance isn't an allergy, you just don't produce enough enzyme to break lactose down, so low lactose products or enzyme supplements can help)