The Most Common Allergy In The World

Urushiol is a molecule found in poison ivy and poison oak that causes allergic reactions in humans. Although not inherently dangerous, it tricks the immune system into responding as if it were a threat. This reaction is similar to other allergies, where harmless substances trigger an immune response. Urushiol is the most common allergy, affecting 85% of people, yet it doesn't seem to have evolved as a defense mechanism. The reason why urushiol affects humans and not other animals remains a mystery.

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