Seasonal non-allergic rhinitis (SNAR)--a new disease entity? A clinical and immunological comparison between SNAR, seasonal allergic rhinitis and persistent non-allergic rhinitis.

We have earlier described a group of patients suffering from rhino-conjunctivitis during the early pollen season, but with negative allergological investigation. The present study aimed to evaluate this syndrome called Seasonal Non-Allergic Rhinitis (SNAR). Seventeen patients with SNAR were compared with 20 patients with seasonal allergic rhinitis (SAR) and 13 patients with persistent non-allergic rhinitis (PNAR). They were analyzed with skin prick tests (SPT) and nasal provocation tests (NPT) with pollen extracts, and for IgE antibodies in serum and inflammation mediators in nasal lavage. Daily symptoms and medicine consumption were recorded. Late reactions after SPT occurred in two SNAR, eight SAR and two PNAR patients. Weak immediate and late reactions after NPT were induced in 3/15 and 7/15 SNAR patients, respectively, and in 1/13 and 5/13 PNAR patients. All SAR patients had immediate and 9/18 had late reactions. The total IgE levels were lower in SNAR compared to SAR. In the SNAR group 1/15 was positive in Phadiatop®. Increased tryptase levels after NPT were only observed in SAR. The SNAR patients had high daily symptom scores already before birch pollen season. Sneezing was more common in SNAR and SAR than in PNAR; eye-symptoms more prominent in SAR than in SNAR or PNAR. SNAR seems to be different from SAR and PNAR regarding immunological mechanism and symptom period. We conclude that the cause of SNAR is unknown.