One of the most common things that people are exposed to while clearing up their backyard are plants of the toxicodendron genus. They can easily mix in with the leaves and twigs that you are picking up, and the next thing you know, you have an itchy rash that is spreading. The three most common plants are poison ivy, sumac and oak. The reason for the irritation they cause is an oil that they contain. The reason why it is so easy to be exposed to it, is that it sticks to your skin, clothing and other items, and will still cause a rash when it is touched much later.
You should never burn these plants, because the smoke when inhaled can cause serious problems in your throat and lungs. Even if you are wearing a mask to protect yourself, the smoke can travel into your home, or into your neighbor’s yard and cause trouble.
If you are uncertain whether these plants grow in your backyard or not, you should be on the safe side and wear protective clothing that covers you well.