As she was about to leave the ­office, the retired social worker turned to me. “You didn’t say anything about my black and blues,” she said, pointing to several bluish-purple, quarter-sized spots on her forearms.

Bruises, the breakage of tiny blood vessels near the skin’s surface that result in a blackish-bluish-purplish discoloration, are a common complaint among patients in their 60s and beyond.

And distinguishing between innocent bruising and bruising that’s due to serious, sometimes life-threatening, diseases can be a challenge, even to an experienced practitioner.

Here, when you can ignore the bruises and when to call your physician.  

Most Bruises Are Harmless

Studies have shown that up to 55 percent of healthy people bruise easily. It's the reason for—or part of—many office visits.

Usually, the bruises don't signal a bigger issue—though patients who bruise easily are often annoyed by the appearance of black and blues, and some wear long sleeves or makeup on their legs to cover them up.

People of any age may simply be bruise-prone, always bumping into objects such as railings and open drawers.

In older adults, bruises known as senile purpura—seen in skin that's been thinned by long exposure to the sun and environment, and without the protective cushion of fat that disappears as the years go by—is almost always the result of an insignificant trauma.

These black and blues (“ecchy­moses” in medicalese) usually number not more than two or three on an arm or leg and are not bigger than the size of a quarter.

As the blood is gradually reabsorbed, the pigments are broken down and fade to a greenish hue, then yellow, and then they’re gone.

But Some Bruises Reveal Problems

The ability of blood to clot properly usually prevents black and blues from enlarging. But certain medications or conditions that interfere with this can result in larger ecchymoses, including some on the torso.

Medications that can have this effect include those that thin the blood (aspirin; nonsteroidal anti-inflammatory drugs, such as ibuprofen and naproxen; warfarin; and newer oral anti-clotting agents) and ­dietary supplements such as fish oil, ginger, Ginkgo biloba, and ginseng.

The same can happen when the skin undergoes excessive thinning—with, for example, the prolonged use of corticosteroids—or when the body produces excessive amounts of cortisol, as with Cushing’s disease and Cushing’s syndrome.

Almost any drug, including antibiotics, antidepressants, and tranquilizers, can cause a decrease in blood platelets—which are cells necessary for clotting.

Platelet disorders can also cause ecchy­moses. More characteristic of platelet problems are tiny red dots on the legs called petechiae. These look quite different from ecchymoses, which have a blotchy appearance.

Bone-marrow disease, such as leukemia (acute and chronic) and myelodysplastic syndromes, as well as liver and kidney disease, can all cause clotting problems and bleeding into the skin. 

And when benign ecchymoses ­occur on the face, neck, chest, or abdomen, a cause other than the aging process has to be considered. In particular, bruises on sites other than the arms and legs—especially the face and neck—should prompt questions about abuse.

When to Call the Doctor

Contact your doctor in the following five instances:

  1.  Ecchymoses or petechiae appear within a month of starting a new prescription or over-the-counter medication or supplement.
  2. Bruises are numerous, large, or on parts of your body other than arms and legs.
  3. Bruises are accompanied by bleeding elsewhere (gums, stools, urine).
  4. In addition to noticing that you bruise easily, you have a family history of a bleeding disorder.
  5. You are at all concerned about your bruising. Blood tests such as a normal complete blood count, prothrombin time (also referred to as INR), and activated partial thromboplastin time should provide reassurance by ruling out the majority of clotting disorders.