I spend a great deal of time in the woods and fortunately I have never been affected by poison ivy, poison oak, or poison sumac before. For a crew of students working under my direction this summer they were not as fortunate. Recently, somewhere, somehow, they all came in contact with one of the three poison plants. None of them recall seeing the plant but they all have visible proof on there arms, gross looking, reddish blisters, of various sizes.
So why am I telling you this? Well I always encourage people to get out and explore the back woods but I would be neglectful if I simply sent you out there without showing you what these three poisons look like. The only true way to avoid these poisons is avoid them so learn how to identify them.
Poison ivy: This poison is found throughout most of North America but is rare in desert and mountain terrains. Typically for this plant use the old addage "leaves of three let it be" but it is a versatile plant and can look like a shrub, a flower, or a vine. The leaves can vary in color from green, red, orange, or yellow depending on the season and location of the plant. The leaves will have a waxy texture with two leaves opposite and the third on a longer stem to the top. Poison ivy also produces various berries which can be hard to see thanks to the leaves which can be up to 4"long. If you do not know what poison ivy looks like I suggest you do a Google search for it just to be safe. (Photo courtesy of http://www.trails.com/)
Poison Oak: From what I can find, and keep in mind I'm no professional so I encourage you to look for yourself, poison oak is not found in eastern Canada. It is found in western Canada however as well as the Eastern US, as far north as New Jersey. So just to be safe I have posted a picture of it here. (Photo courtesy of http://www.add.org/)
Posion Sumac: This poisonous plant is found in Atlantic Canada and differs from the previous two in that it does not have a trifoliate leaf structure. It typically has 7-13 leaflets in a compound opposite formation. It often grows in wet areas near bogs or rivers. The branches of the poison sumac, not to be confused with staghorn sumac, are often reddish in color and the berries are a hard white color. Staghorn sumac leaves are serated while the poison sumac leaf is smooth, the berries are also different as the staghorn has reddish fruit. (photo courtesy http://www.add.org/)
I strongly encourage you, if your worried about coming into contact with any of these plants, to investigate them. If you do come into contact with them be sure to wash your clothing as the urushiol (the oil that causes the skin irritation) can also be spread through secondary contact of clothing or tools that come in contact with the substance.
Cures for these poisonous plants are typically anti-inflammatory creams (hydrocortisones). I'm no doctor so I suggest if you come in contact with any of these plants that you seek out medical help.
I hope this helps you feel more comfortable in the back country of Atlantic Canada.