Chronic stress, or a constant stress experienced over a prolonged period of time, can contribute to long-term problems for heart and blood vessels. The consistent and ongoing increase in heart rate, and the elevated levels of stress hormones and of blood pressure, can take a toll on the body.
Excess Tearing. The most common cause of tear stains in dogs is excess tearing or epiphora, which makes the hair and skin around the eyes damp. This can lead to the growth of bacteria and yeast. Red yeast, which produces a reddish brown discoloration of the face, is a common cause of tear stain problems.
Algae is more likely to grow on shaded roof sections (probably the cause of black stains on the lower roof in the photo at above right), while asphalt shingle bleed-through stains more often appear to emanate from single points regardless of sun or shade exposure (probably the cause of stains in the photo at above left).