Lahore offers street food that is not only delicious but also extremely cheap. But in order to enjoy the food you must (I am saying MUST) have you own disposable plates and spoon in your daypack, and always drink bottled water. Do not ruin your vacations by having bad stomach.
The best way to avoid stomach upsets is to always be sure that water you drink has been filtered or boiled. Bottled water is fine but it costs nothing to boil a pot of water. After boiling it directly in the pot, use a cloth to filter through the calcium and things that float to the top of the pot.
Its a good idea to hit the local pharmacy and ask for some 'motion' stopping pills should it begin to happen. Just say Medicine Stop Motion, and they will understand even in english! It shouldn't cost more than 100 Rs for a big pack of them and keep them handy.
Another important thing to understand is that eating outside and public places is not always the freshest and healthiest choice. In fact, if its not a decent hotel or seemingly upscale place, then its not a good idea to eat there. Roti shops and tika bar-b-que stalls however, are usually generally clean as they are most popular with locals and frequented all the time. If you are in a area where there is a Dunkin Donuts, Pizza Hut, or McDonalds then that is usually the best option for foreignors as they have higher standards for food services.
Finally, another way to avoid stomach troubles is to be sure and eat yogurt along with any dishes that may seem a bit too spicy. If possible ask for PLAIN rice like a chicken fried rice, anything continental is likely to be less spicy. If you can't stomach anything then simply ask for a cooked egg and eat it with sliced toast or roti/naan of choice. It is most mild on the stomach.
The Lahore pollution (dust, they call it) can be a real drag when you have a cold, and you need something to settle yourself down. I discovered Joshanda herbal tea, which is about 5 Pk rupees per packet. Drink three of these a day, and it helps. I got a few boxes of the packets from an herbal medicine shop in Model Town, but any medicine shop should carry it.
Buy Nestle water. Or have it boiled before you drink it. But even that didn't save me from an upset stomach. Or maybe it was pshychological.
Who knows. But to be on the safe side, stick to bottled water.
Stomach upset problems are the most common. Here is a permanent solution: But you must Trust Me!
Go to a medical pharmacy and ask for a local medicine (sort off) 'Marhaba Isbagol Husk' Manufacturer is Qarshi.
Its too Good and no side effect, just have it with water its pure herbal and it stops the constipation at once and absorb all the dirty liquid in your intestines. It always works in ordinary days even. Try it and Trust Me! ;-)