Earlier this month, I wrote a post that talked about how wildlife uses poison ivy berries. I had written: "Only humans suffer allergic reactions from oils on the plant, and it does not affect the other wildlife". My co-blogger, Dan Barringer, emailed me to point out that it isn't actually an allergic reaction, but a dermatitis. (He also admitted that he wasn't sure what the differences were.)
So on Tuesday, I asked Virgina Derbyshire. Not only is she the best all around naturalist that I know, but her training in the medical field is equally impressive. "Ask Virginia, she'll know!" is a common comment on our nature walks (offered by the other very good naturalists in the group). Well, she did know.
If I understood her correctly, there are different types of white blood cells in our bodies to protect us from different types of assaults. There are white blood cells that combat allergens by "marshaling" anti-histamines to the site. When it comes to poison ivy, different types of white blood cells are activated to address hyper-sensitivity. If the rash blisters, an even different type of white blood cell is utilized to fight off infection. Because they are not the same kind of white blood cells that affect allergens, a poison ivy rash can't really be called an allergic reaction. I can't recall any of the different types of white blood cells that Virginia told us about, but I now understand the difference between an allergic reaction and what happens to when you get a rash from poison ivy.