Answer:
Poison ivy rash is caused by contact with poison ivy, a plant that grows almost everywhere in the United States. The sap of the poison ivy plant, also known as Toxicodendron radicans, contains an oil called urushiol. This is the irritant that causes an allergic reaction and rash.
You don’t even have to come in direct contact with the plant to have a reaction. The oil can linger on your gardening equipment, golf clubs, or even your shoes. Brushing against the plant — or anything that’s touched it — can result in skin irritation, pain, and itching.
Jared might have told him about his activities similar to the ones like gardening etc. by which Jared's physician use to make a diagnosis.
He told doctor that he just returned from camp this clearly indicates that he might get in touch with plants .
