This study aside... Nicotine has been proven to have a profound effect on the immune system inhibiting both the innate and adaptive immune responses. Nicotine affects both humoral and cell-mediated branches of the immune system and produces an altered immune response that is characterized by a decrease in inflammation, a decreased antibody response and a reduction in T cell-receptor-mediated signaling. A multitude of studies have been done on the immunosuppresive and anti-inflammatory effect of nicotine in treating autoimmune disorders such as MS, RA, Chrons, Alzheimers, Parkinson's and others.
Which could explain why smoking seemed to alleviate a lot of my allergy symptoms -- not all, they didn't vanish, but they did seem a lot milder than before I smoked.
Andria