Have you ever phoned your doctor about a sudden medical concern­, one that had you predicting a trip to the hospital, emergency surgery, or even impending death?

When an apparently healthy body malfunctions in an unexpected or mysterious way, many people fear the worst. But sometimes there's a simple explanation for worrisome symptoms.

Here are five common medical conditions that may seem omi­nous, and the benign factors that are often behind them:

Black Stools

Not long ago, a 53-year-old accountant called me in a mild panic. He had passed a black stool and was worried that he might be bleeding from colon cancer.

A rectal exam did indeed reveal black stool, but the specimen was negative when tested for blood.

The culprit was bismuth subsalicylate, the active ingredient in Pepto-Bismol, which he had taken for an upset stomach a day earlier.

Other nonworrisome causes of dark stools include iron tablets and certain dark-colored foods, notably beets, blackberries, blueberries, and a more recent addition to my list, squid-ink pasta.

Breathlessness or 'Sighing'

If you've experienced the sensation of ­being unable to take a deep enough breath, you know how uncomfortable it can be.

These "sighing" respirations, which can occur several times per hour, can lead people to fear that each breath may be their last.

But lung and heart function are invariably normal. Those sighing breaths are, paradoxically, a physical manifestation of underlying anxiety.

And the sighs often subside on their own with sufficient reassurance from your doctor that all is well. If not, that underlying anxiety should be treated.

Flaming Red Eyes

A subconjunctival hemorrhage sounds horrendous and looks even worse—with the white of an eye suddenly turning flaming red.

Those experiencing this may worry about eye disease or bleeding disorders, but the hemorrhage is harmless.

The redness is due to the rupture of a tiny capillary under the conjunctiva, the delicate transparent membrane that covers the white of the eye.

It can be caused by any effort that acutely raises pressure inside the head, such as bending over, coughing, sneezing, straining (as with weight­lifting or a bowel movement), or an orgasm.

No treatment is needed; the blood will slowly reabsorb on its own within a couple of weeks.

Orange Skin

You might become concerned if a friend notes that your skin, especially on the palms, is orange-yellow. Could it be jaundice caused by hepatitis or liver cancer?

Not if the whites of your eyes and your urine are normal in color.

What you have is carotenemia, a benign yellow-orange staining of the skin that comes from eating a lot of carrots or other veggies high in beta-carotene, or from taking beta-carotene supplements.

Chest Tenderness

This uncomfortable chest lump generally comes to medical attention during the summer or after a patient, almost always a man, returns from a tropical paradise during the winter.

Out of nowhere, it seems, there's a painful protuberance at the lower end of the breastbone or sternum.

Actually, the "lump" is the quarter-sized cartilaginous end of the bony sternum, called the xiphoid process.

In most men, this projects forward a bit and becomes tender when subjected to constant pressure from, for instance, lying facedown on a sandy beach for hours on end.

The sensitivity subsides within a week or so if that prone position is avoided.

All’s Well That Ends Well

The accountant was relieved to learn that he wasn't bleeding internally—and mildly embarrassed that he hadn't read the label on the Pepto-Bismol, which warned of the possibility of black stools.

But because his father had died of colon cancer, he was referred for a colonoscopy, which found a pre­cancerous tumor that was removed.

So never be embarrassed about calling your doctor when you notice an unusual medical symptom, even if you suspect that reassurance is the only treatment required. The accountant's failure to read that Pepto-Bismol label may have saved his life.