The Most Common Allergy In The World

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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.

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Khaled Marwa, Noah P. Kondamudi (2021) Type IV Hypersensitivity Reaction. StatPearls. Retrieved from:

John Barrat (2014), A Poison Ivy Primer, Smithsonian Retrieved from:

Florian Winau (2021) Personal Communication. Department of Pediatrics, Harvard Medical School.

Tiffany Scharschmidt (2021) Personal Communication. Department of Dermatology, UCSF Medical School.

Yesul Kim, Alexandra Flamm, Mahmoud A. ElSohly, Daniel H. Kaplan, Raymond J. Hage Jr, Curtis P. Hamann, and James G. Marks Jr (2019). Poison Ivy, Oak, and Sumac Dermatitis: What Is Known and What Is New? Dermatitis. 30: 3 (183-190). Retrieved from: