A scar on the upper lid can cause discomfort as some patients feel the scar as they blink.

And the scars from heart attacks can cause arrhythmias and congestive heart failure.

Superficial scars caused by acne, surgery, or trauma that are not growing or that are getting thicker.

Exposing scars to the sun can cause them to darken and slow the healing process, says Alster.

A half-inch curved scar caused a quarter moon of silver to shine smoothly two inches below her elbow.

The scar may cause psychological trauma on the persons affected.

"My scars have been causing me discomfort," said the Moidart.

These atmospheric scars of international shipping are causing concern among scientists studying global warming.

The sergeant turned to Polly and grinned, which made his scars move oddly and caused a tremor to shake all his chins.

A hypertrophic scar can cause restricted movement of muscles, joints, and tendons (contracture ).