FOUR AILMENTS THAT ‘ DON’ T EXIST ’

1 STOMACH FLU

If you suffer from vomiting and diarrhea, it’s not influenza, Jill Swartz, an urgent-care doctor in New York, tells Prevention Magazine. The flu virus causes fever, congestion and sore throat. The stomach issues are probably from gastroenteritis, which is a different virus.

2 WALKING PNEUMONIA

Doctors use the term, but it’s “something of a catch-all rather than an exact diagnosis,” Swartz says, trotted out when you have a chronic cough and doctors don’t know why.

3 GLUTEN ALLERGY

Yes, gluten can make some people feel sick, but what’s going on is not an allergy. “Celiac disease ... is an immune response to gluten, not an allergy like we think about a peanut allergy,” says allergist Janna Tuck. And you might just have a sensitivity.

4 HEAD COLD

No different from any common cold. (The same goes for “chest cold.”) You’re just describing where you happen to notice the symptoms.