Poison oak has leaves that look like oak leaves, usually with three leaflets but sometimes up to seven leaflets per leaf group. It grows as a vine or a shrub. Poison oak is more common in the western United States, but it is also found in the eastern United States and, rarely, in the Midwest.
Poison sumac has 7 to 13 leaflets per leaf stem. The leaves have smooth edges and pointed tips. Poison sumac grows as a shrub or small tree. It is found in wooded, swampy areas, such as Florida and parts of other southeastern states, and in wet, wooded areas in the northern United States.
Poison ivy usually has three broad, spoon-shaped leaves or leaflets (“Leaves of three? Let it be!”), but it can have more. It may grow as a climbing or low, spreading vine that sprawls through grass (more common in the eastern United States) or as a shrub (more common in the northern United States, Canada, and the Great Lakes region). ~content provided by Healthwise
The subsequent itching, rash, and blisters that come from contacting these plants. These oils can exist for years on tools and such if not washed off. These oils can be spread with contact. They can get on your hands and be spread to everything you touch if you don’t wash it off. Additionally, oils can get on your clothes and can be transmitted to whoever touches them.
It takes typically 48 hours from contact to reaction with the highest oil concentration showing first. Because of this “expanding development”, people have mistakenly thought that once the blisters weep, they can spread.
There is no cure for poison ivy/oak/sumac. Just like cold medicines, there are only ways to alleviate the symptoms. I personally just wait it out, but many use calamine lotion or other anti-itch creams. Although medically told not to, I also run hot water (as hot as you can stand) over the infected area. This causes it to itch like crazy, but you get a good reprieve from the itch for a while afterwords.
To avoid coming in contact with any of these, stay away from greenery. If you can’t do that, then cover all exposed skin and wash tools after use. Take care when removing clothes not to touch the outer portion and either wash them immediately or invert them so no to spread the oils to others.
In my line of work, I can’t avoid the poisons all the time, and I find that the 2 or 3 cases I get each year are overshadowed by the heat so I wear shorts. (If you haven’t figured it out, I have a case of poison ivy right now on my calves/shins and my left wrist.)