Smoking cigarettes is vaso-constrictive. This means it makes your blood vessels, like the ones present in your gums, tighten up. As soon as you stop smoking and make the switch to vaping, your gums can bleed if there is gum disease present. The vasoconstrictive effects of smoking is no longer there.

When switching to vaping some people have the unfortunate side effect of bleeding gums. This can be confusing, as this may never have happened when you were smoking. What is going on? Now every time you brush your teeth, there's blood.
MRI scans of people smoking have shown the blood supply to their fingers decreases by a considerable amount and as mentioned, the same will be happening to your gums. Any gum disease that is there due to the smoking (there will be some, usually with a build up of plaque) is masked due to the vasoconstrictive effect of the tobacco.c
Why Do My Gums Bleed When Vaping?
Updated: 20th Jan 2020
The smoking has been masking your problem, stopping allows you to see your true gum condition. The blood vessels are no longer squeezed, they can function normally. Delivering oxygen and nutrient rich blood back to your poor gums. The bleeding is a good thing, warning you about the gum disease meaning you can now do something about it!
The obvious first step is to visit your dentist. Get a professional clean, start flossing after you clean your teeth and definitely don't start smoking cigarettes again.

If you leave gum disease to develop, it can eventually dissolve away your jawbone. Your teeth fall out…not a good look!
How Do I Prevent My Gums Bleeding When Vaping?
Both scientific and anecdotal evidence suggests that smokers who stop or switch to an e-cig, experience an increase in gum bleeding. It can take a little time for your gums to restore themselves back to normal, but well worth the wait if it prevents other problems.
So stop smoking permanently, brush 2-3 times a day (not forgetting mouthwash and floss) and visit your dentist. You’ve gotten rid of the fag breath, you don’t want rotten teeth instead!