These two terms are used interchangeably to describe a worsening of a medical condition that, depending on state statutes, can make very little or a major difference in payment of medical and indemnity benefits.
Aggravation is an increase in the severity of a pre-existing condition where the underlying pathology is permanently moved to a higher level.
Example: An employee with degenerative disc disease (normal aging) occasionally has a backache, but lives with the discomfort. The employee suffers a back injury while lifting a heavy object at work. The pre-existing degenerative disc disease is aggravated when the injury causes the employee to experience permanently a higher level of back discomfort or pain.
Exacerbation is a temporary increase in the symptoms of a pre-existing condition that returns to its prior level within a reasonable period of time.
Example: The employee completely recovers from the injury, returning to the prior level of function, but still with an occasional backache. The worker suffered an exacerbation of the pre-existing condition.