All three of these conditions are extremely uncomfortable. An allergic reaction is caused by your skin when you are touched by any of these plants. Your skin creates an inflammatory reaction, causing redness, itching, rashes and even blisters. You will usually notice the inflammatory reaction within 1-2 days after direct exposure, and the discomfort may last up to 21 days. There are numerous treatments that Dr. Nicolaides and his team can perform, and it is best to make an appointment for proper evaluation.