Parents tend to take their children to the doctor at the earliest sign of illness. But it's easy to forget that, even as adults, some sicknesses need medical attention. If any of these signs appear, it's probably best to head to a physician. Difficulty Breathing Having a bit of congestion during a cold is normal. But when this symptom escalates, especially if it becomes difficult to pull in air, it can be the sign of either an intense cold or...