What are the differences between poison ivy and impetigo?

Allergy vs infection: Poison ivy is an allergic reaction, not contagious and will resolve over time even if untreated. After each addition exposure to poison ivy (or poison oak), the reaction is stronger. Impetigo is an infection, typically due to staph aureus, and is contagious. Impetigo needs to be treated with an antibiotic.

Allergy vs Infection: Poison ivy is an allergy to the urushiol oil in the plant. Impetigo is a bacterial infection of the skin. Sometimes they occur together - that is, poison ivy can become secondarily infected and turn into impetigo. Poison ivy is treated with anti-inflammatories, impetigo with antibiotics - so it's important to differentiate. See a dermatologist.