It will depend on how extensive your rash is. Generally, poison ivy is more annoying than painful. However, if you scratch the rash enough that it bleeds, it can be really painful.
Also, if poison ivy has been burned and you're breathing in that smoke, it can get in your lungs and eyes and cause problems. This can be one of the most painful ways a person develops irritation from poison ivy.
How long does it take to recover?
It depends. You'll want to keep from scratching the rash. You don't want to break open the blisters. Bacteria from under your fingernails can get into the blisters and cause an infection. After about a week, though, the blisters should start drying up, and the rash should go away. However, if you have a large rash across your body, it could take longer.
When should a person seek medical attention?
Usually, a rash from poison ivy doesn't merit a trip to the doctor. However, if you develop a fever higher than 100 degrees or if the rash covers large areas of your body, you might want to contact your doctor. Also, if the rash is in your eyes, mouth or genitals, you might want to seek medical attention. Also, if pus starts coming from the blisters or if the rash does not get better after a few days, you should talk with your doctor.
Source: Whitney Kemp, education coordinator at the Oklahoma Poison Control Center; American Academy of Family Physicians.