I keep seeing headlines on facebook about depression being an allergic reaction to inflammation. The thing is, there are several kinds of allergies, but I if you track these blogs and articles back to actual scientists I don’t think any of them are saying it’s an allergic reaction to inflammation. Inflammation is part of allergic reaction and part of immune response. I only really understood this after microbiology. We had this youtube in pathophysiology that gives a good scope on the complexity: https://www.youtube.com/watch?v=zQGOcOUBi6s (Why you are still alive by Kurzegesacht , IIRC)
There are may kinds of allergies, but all involve a molecular trigger in combination with specific antibody classes, which is what the bad science writing on depression and inflammation is promoting. We do not react allergically to “inflammation” in this sense. Inflammation, in the animation above, is the message sent by immune cells for blood vessels to expand and cause swelling. It is hopefully locallized. It can happen in the brain, unfortunately. It is likely to happen in your gut, which utilizes as much seratonin as your brain.
What the better blogs will say is that we can’t say which way the correlation goes, so don’t start popping advil and expect your depression to go away (plus, it’s bad for your liver and kidneys). The easier explanation is that the foods we eat to push seratonin, sugar, chocolate and salt with fat, all promote inflammation (I believe, by pushing the phosphate buffer balance in our cells.)
And this would explain why exercise and eating vegetables helps reduce inflammation. Exercise pushes the phosphate balance back away from insulin resistance. Vegetables provide potassium and nitrogen, which oppose the effects of sodium and superoxides in cell membrane responsiveness.
But comfort foods are known to cause inflammation. So any theory on inflammation causing depression would need to that variable first. It’s not allergies instead of seratonin. It’s that the immune system interacts with the seratonin systems.
Image from wikipedia IgM