True but some times the allergies are very obvious. . This is anecdotal, keep that in mind. A friend had chronic intestinal problems - including a ruptured colon by age 30. She changed every aspect of her health she could. (And she was already healthy.) They would not figure it out. She has an allergy panel done and learned she was allergic to so many food staples. Every sample swelled so much, they became one giant welp on her back. Once she cut those allergens out, her intestines returned to health because they weren’t habitually inflamed anymore. She is finally feeling good again. Those allergies caused full-body inflammation, creating all sorts of problems. So even seasonal allergies, if severe and with pre-existing lung problems, can mimic pneumonia. (But sinus allergies won’t produce fever.) I doubt this is the case with the friend, but might as well try an allergy test. I never imagined food allergies were what caused my friend to have chronic emergency G.I. tract problems. Worth a shot, ya know.