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Speaker 1: I'm Marshall Brain with today's question. What causes poison ivy blisters?
Speaker 1: The rash that you get from poison ivy is caused
Speaker 1: by a chemical in this sap called urushial. This chemical
Speaker 1: penetrates the outer layer of skin until it hits the dermists,
Speaker 1: and in the dermist an allergic reaction occurs. From that definition,
Speaker 1: there are a number of things that you can deduce
Speaker 1: about poison ivy. First of all, not all people get
Speaker 1: poison ivy. If your body doesn't mount an allergic reaction,
Speaker 1: then you can swim in poison ivy and it will
Speaker 1: have no effect. It turns out, however, that the majority
Speaker 1: of people's immune systems react to this chemical after several exposures. Second,
Speaker 1: you can't get poison ivy unless you come in contact
Speaker 1: with the SAP that contains rushial. However, it is incredibly
Speaker 1: easy to come in contact with that sap. You can
Speaker 1: get it from the plants itself. You can get it
Speaker 1: from touching your shoes or pants if they have rubbed
Speaker 1: against poison ivy plants. You can get it from your
Speaker 1: dogs or your cats fir if they walk through poison ivy.
Speaker 1: The rushi all has to penetrate the skin to get
Speaker 1: to the dermist, so thin skin will show symptoms before
Speaker 1: thick skin will. And finally, rushill does not spread through
Speaker 1: the body. The blisters that form are not contagious. They
Speaker 1: don't contain any more of the chemical. If you come
Speaker 1: in contact with poison ivy, washing off the SAP will
Speaker 1: limit your reaction to it, but you have to wash
Speaker 1: it off before any significant penetration occurs. The mechanism that
Speaker 1: causes the itching and swelling is a complex immune response
Speaker 1: to the chemical, as in any allergic reaction. What's happening
Speaker 1: is that your body's immune system is overreacting to the chemical.
Speaker 1: It mounts a huge defense to the arushial, which causes
Speaker 1: all the swelling and inflammation in the skins. Do you
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Speaker 1: please send me an email at podcast at how stuff
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