You've got it exactly right. It explains why diet, stress, digestion, and SD are all related.
Diet is very important because a bad one triggers high levels of cortisol. Over- and under-eating, as well as eating bad food, causes physical stress. Exercising too hard on an empty or full stomach is also very bad.
Emotional stress, too, creates a cortisol spike.
Some info from the Mayo Clinic:
"Cortisol, the primary stress hormone, increases sugars (glucose) in the bloodstream, enhances your brain's use of glucose and increases the availability of substances that repair tissues. Cortisol also curbs functions that would be nonessential or detrimental in a fight-or-flight situation. It alters immune system responses and suppresses the digestive system, the reproductive system and growth processes."
And a quote from SkinID:
"During times of stress, cortisol slows down your immune system to allow your body to redirect energy to muscles and mental functions. Constant stress, however, keeps your immune system suppressed, making your skin more susceptible to infections. A suppressed immune system may also lead to flare-ups of chronic conditions such as psoriasis and eczema. In fact, studies show that controlling stress, nervousness, and anxiety may help prevent flares of eczema."
Thanks for sharing the info. It's an excellent confirmation of what I'm discovering.