You know you have to rush to the ER and call your doctor right away when your chest hurts and you can’t breathe. These are signs you can’t ignore. But some insignificant symptoms that many would dismiss as the result of too much stress are in fact a way for your body to tell you to check your health.

Some diseases people have for some time — completely unaware — and it would be good to pay better attention to potential symptoms. Most of us consider our habits as simply that — habits, sometimes bad. While most people grow out of different habits, not all do — and that could be a sign. Overlooking our habits might allow a disease or condition to go undetected.

You can sometimes smell if you’re ill. Many diseases have a particular odor. Diabetes, for example, can make your urine smell like a sweet fruit. One woman can even smell Parkinson’s. But not everyone has such a unique ability. Most people have to rely on what they know about what’s normal behavior. Sometimes, however, even so-called normal behavior can wreak havoc on our bodies — here are 21 “harmless” habits that are actually aging you faster than you can imagine.

Many people already know that getting cravings even when they’re already full is a sign of junk food overconsumption, but an increased appetite when you just ate can also indicate diabetes. Some habits are hard to recognize as being a sign of a potential health problem, especially if they have been part of your daily routine for years. But it never hurts to pay closer attention.

To create a list of 19 habits that may be masking an underlying health problem, 24/7 Tempo consulted doctors and reviewed scores of research papers and academic studies.

Click here to see 19 ordinary habits that may be signs of serious health problems.