"... The urushiol molecules in poison ivy have the ability to trigger a harmful immune response in most people because the immune system mistakenly labels them as a threat.
To learn more about this topic, start your googling with these keywords:
Allergy: A damaging immune response by the body to a substance.
Allergen: The substance that causes the allergic reaction.
Urushiol: The allergen in poison ivy and poison oak.
Allergic Contact Dermatitis: An allergic response caused by contact with a substance that causes rash or lesions at the site of the exposure.
Langerhans Cell: An immune sentinel that lives in the epidermis of the skin but can travel to nearby lymph nodes.
Helper T Cell: A type of white blood cell that activates immune responses in the body.
Thrush: A white skin rash caused by the fungus candida.
Anaphylaxis: A whole body allergic reaction that can include throat swelling..."