Elf bars are not bad for your lungs, but they can cause some side effects if you eat too many of them. The sugar and caffeine in elf bars can cause a temporary rise in heart rate and blood pressure, and they can also cause some mild digestive issues like bloating and gas. However, if you stick to eating one or two elf bars per day, you shouldn't have any serious side effects. Just remember to eat them in moderation and drink plenty of water to stay hydrated!