Suicide and decompensation of mental illness peak in spring and, to a lesser extent, in fall. Several recent studies reported that suicide and decompensation peaks coincided with spring and fall aeroallergen peaks. Allergic symptoms occur as the result of a complex biochemical cascade initiated by IgE antibodies (sensitization) and allergens (triggers). Animal models have shown molecular/neurochemical changes in the brain, as well as relevant behavioral changes associated with this IgE-mediated biochemical cascade. These factors suggest that seasonal allergy could precipitate suicidality and mood instability. In the current study, we compared the prior suicide attempt and history of decompensation of mood disorders in allergen sensitive vs nonsensitive patients. Further, we compared the ratio of events (attempts and decompensations) during the allergy season to events occurring during the rest of the year. Patients with Major Depressive Disorder or Bipolar I or II Disorder (n=80) were studied. There were no statistical differences in any measurement performed between the allergen sensitive and nonsensitive patients. These negative results are not consistent with recent epidemiological studies supporting a predictive association between allergy and categorical measures of suicidality (ideation, attempts, and completion). Clinical samples are likely not adequate to study less than strong predictive associations with suicide and suicide risk factors.