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Watch for an itchy red rash line 24-48 hours after you contact poison ivy. Check for rash splotches if a contaminated pet or item touched you. Watch for blisters and swelling around the affected area.
The rash might appear earlier if you contact a lot of the urushiol oil. You'll only have a rash where the plant's oil touched your skin, so it often appears in a line. In most cases, the rash will last for about 2-3 days. The rash may spread from scratching if you still have oil on your skin, so the line might not be straight. If you have a rash that's spreading after you scratch it, then it's likely poison ivy or one of its cousins, poison oak and poison sumac. However, keep in mind that other types of rashes can spread as well. The oil from a poison ivy plant can linger on your pet's fur or on clothing that came in contact with the plant. Unfortunately, this oil can cause rashes. If you suspect your pet or other items have contacted poison ivy, look for a splotchy red rash on the affected area.  Wash clothes that came in contact with poison ivy immediately and separately. Handle them as little as possible. If your pets came into contact with poison ivy, wash them immediately. The irritating oil can remain on their fur and spread to things they touch. You should also wash anything you know they touched, as oil could remain on the surface. Pets usually won't develop a rash after contacting poison ivy. You likely won't notice your pet got into poison ivy unless you see them do it or develop a rash yourself after touching the contaminated fur. Blisters are normal with poison ivy rashes, and their size can vary from pin-sized to dime-sized. Your blisters may pop and release a clear fluid, but this is normal and won't spread your rash. You'll also have inflammation as a result of the rash, which can cause swelling.  Blisters usually develop within 1 to 14 days after you encounter the poison ivy.  Never pop blisters on your own! With a poison ivy rash, you'll likely see more swelling than with other types of rashes. Watch for pus coming from the blisters. If you notice pus, then your rash is likely infected and you should see a doctor for treatment as soon as possible.