There are many causes of bleeding gums, but the one thing they all have in common, is that they should all be checked out by your dentist and diagnosed and treated.
The most common cause of bleeding gums, in young people, is early gum disease (“gingivitis”) which is often an easily-treatable condition. The gums that are red, swollen and shiny have been irritated by the germs in plaque on the teeth.
Bleeding gums in older people (especially when a tooth or teeth become loose, or start to move from their normal position) can be a more severe gum disease called “periodontitis”.
Receding gums, or a persistent bad taste or bad breath, are also often signs of more severe gum disease. Both of these problems should be treated by your dentist to prevent teeth being lost.