What is the difference between a rosacea flare up and flushing?

[Guide]

There are two distinct rosacea phenotypes related to flushing and a rosacea flareup: 

Phenotype 1 - Flushing 
Phenotype 2 - Persistent Erythema

It is a common misunderstanding with rosaceans that these two are the same, however, there are indeed some rosaceans who do not flush, hence, the two distinct phenotypes. A rosacea flareup is a more intense outbreak of redness, bumps or pimples. [1] 

Flushing (or blushing) is something that occurs in the general population. Frequent Flushing is a sign (or symptom) of rosacea and usually the distinguishing marker in a rosacea diagnosis. However, not all rosacea sufferers experience frequent flushing or flush (or blush) any more than the general population. But in most cases, frequent flushing is experienced by rosacea sufferers. For many the flush also is accompanied by burning or an episode similar to a hot flash that lingers for a long period. Flushing (or blushing) can exacerbate a rosacea flare up. That is why many use flushing avoidance as a treatment for rosacea. But one could have a flush (or blush) and the episode expires and no rosacea flare up occurs. Yes, this is possible. Just because you flush doesn't necessarily mean you will have a rosacea flareup. But the chances are, if you suffer from rosacea, flushing will exacerbate a rosacea flare up.

Phenotypes have replaced subtypes. 
What is the difference between a Trigger, a Tripwire, a Flareup, and a Flush?
More on Flushing

End Notes

[1] Trigger, Tripwire, Flare up, Flush