Some people are very allergic to these plants, and may need to see a dermatologist if they get a rash. When you come into contact with the oil from a poison ivy, oak, or sumac plant, you may break out in an allergic rash. You can get an allergic rash almost anywhere on your body, and it can take 10 days or longer to heal. Although we aren't born allergic to poisonous plants, almost all of us will eventually have an allergic reaction to them. Even if you've never had a poison-plant rash, you still need to be very careful, because only a small number of people don't get any reaction at all.
Some people are extra sensitive to poisonous plants.
They develop a very bad rash with blisters and extreme swelling on their face, arms, legs, and genitals. People with painful cases need to see a dermatologist right away. Those with extreme swelling, may need to go to an emergency room. What to do about poisonous plants. If you're going to be where you think poison-plants may grow, wear long pants and long sleeves, boots, and gloves.