Allergic Contact Dermatitis Secondary to Smoke

This was a brutally tough question.  This patient was helping her mom and dad clear some brush from their property near San Antonio, and she came down with this mysterious swelling and itching on her face. At first, I thought it was urticarial or angioedematous, but the problem was that there was no lip swelling, the distribution was asymmetrical and somewhat patterned.  Using those clues, I moved away from hives and angioedema and started looking for a cause for the swelling.  Knowing now what you know, what is your best guess for the etiologic agent given these clues? One point.

Addendum:  Most of you got this right after the above clues were revealed.  The patient's parents had gathered up all the brush and weeds (and poison ivy) from the land they were clearing, started a bonfire and our patient walked through the smoke, with her left side facing the bonfire.  Therefore, the most affected side, her left, got the biggest dose of the toxicodendron dose from the smoke.

The take home message is this, as if I haven't said it before:  Trust your eyes.  If it doesn't add up with the story, ask leading questions, and don't let the patient drive the interview.  In this case, only after I figured out that it was an aerosolized allergen did the patient and parents admit as to what really happened.  Now that you know the story, the picture makes a lot more sense.  Trust your eyes.