how long does poison ivy last : Poison ivy rash typically lasts one to three weeks: Mild Rash: Mild cases may resolve in a week or less with home remedies. Severe Rash: Severe cases can persist for up to three weeks or longer. Treatment: Use calamine lotion, cold compresses, or over-the-counter creams to relieve symptoms. Avoid Scratching: Scratching can worsen the rash and prolong healing. See a Doctor: If the rash is severe or covers a large area, consult a doctor for appropriate treatment.