Gum recession usually occurs in response to gum inflammation. This is the result of a build up of bacterial deposits called plaque or (when calcified) calculus.
Bleeding of your gums when brushing is a sign of gum inflammation.
Sometimes recession is caused by excessive brushing, using a hard toothbrush or incorrect technique.
Recession of the gum exposes the root surface of the tooth. This has no protective layer of enamel and can be sensitive to temperature changes, especially cold, air or being touched.
If you experience these symptoms you should consult a dentist as these symptoms are often caused by decay or a cracked tooth. These will require treatment.
If no decay or cracks are identified often this sensitivity will resolve spontaneously but if it persists you may find desensitising toothpaste may provide some relief.
Prevention is always the best approach. A regular scale and clean is the most effective way of reducing the rate of gum recession. If recession continues then the teeth may become loose and even fall out. It is one of the most common causes of tooth loss.