It's true that stress causes acne, however stress itself is not the main reason behind the breakout, we can look at it as a contributor to a series of bad habits and unhealthy activities.
First thing we need to know is, what is stress?
Stress, is any form of physical, emotional and mental strain. We can add in a bunch of highfalutin words and complex medical terms but at the end of the day it all boils down to the taxation of the body, mind and emotions.
Examples of emotional stress are, fidgeting too much over relationship problems, worrying over the health of certain loved ones, anxiety over huge projects and responsibilities etc.. moreover, with physical stress, it has something to do with vices, lack of sleep, demanding work schedule and anything and everything that pushes your body off its limit and capacity.
According to a skin specialist named Sonya Dakar, The body responds to stress by directing blood flow and oxygen to areas vital for fighting the stress, and withdraws from other areas, including the skin. The skin subsequently becomes starved of blood and oxygen, making it dehydrated, dull, lifeless, and prone to clogged pores and breakouts.
There you have it, myth busted.