Prior to talking about how the itching sensation that hives can cause has been linked to a particular neural pathway, I said I was going to step back at some point and address how and why hives form, since I had conveniently skipped over that part.
So I am rebooting this series of posts to address these important questions that those who have had hives want desperately answered. Hives are such a mysterious occurrence, though, that any one individual may never understand why they happened to him/her in particular.
This graphic is a diagram of the cross-section of the skin. What you need to know is that there are many layers of the skin, and through them all, blood vessels are found. Blood vessels are the highways through which nutrients and other vital molecules travel to reach organs and tissues throughout our body. What may not be obvious is that the skin is an organ; in fact, it’s our largest organ, and it too, needs nourishment, it needs to communicate with the brain, and it needs to repair itself and dispose waste.
That’s where the blood vessels come in. We can think of blood vessels as pipes, and in general they are impervious tubing that keep blood from spilling everywhere. For the larger vessels in our body, this is imperviousness holds true. But then how do molecules trying to reach the tissues or organs get from the vessel to the tissue or organ?
This is where blood vessels get really interesting, because theya re not all alike in structure! The largest vessels start out as multi-layered tubing, with two rings of musculature that can dilate or contract them. As they get smaller and smaller, in order to reach all the minute places in our body, they lose these muscle layers. What’s more, the cells that normally line the tubing and help to maintain their characteristic of imperviousness, actually change to a swiss-cheese type cell. These gaps in the cells’ architecture allow the miniscule molecules and chemicals to leave the vessel and go to the organ or tissue, as well as allow molecules from those tissues or organs to get back into the vessel and travel elsewhere.
This pipeline system works beautifully, until an area of tissue or an organ receives too much of a signal from our immune system. So the question I leave with you for this post, is, can you guess what might be happening in the case where our immune system has been “over-triggered” by some sort of pathogen or allergen, that could then lead to the formation of a hive