Black Spot Poison Ivy

I love learning something new in medicine and this was a new one for me...black spot poison ivy.   Poison ivy (also known as rhus dermatitis) is a common contact allergic dermatitis.  Like poison oak and poison sumac, the chemical that causes a reaction is called urushiol.  When this plant sap touches the skin a pruritic (itchy) red rash appears with little blisters that are often in a line.