Humans, like all life, are sensitive to their environment. Mentally ill or unstable individuals can be triggered into impulsive and violent activities from spikes in serum serotonin. Serum histamine level is directly proportional to environmental allergen levels, but serum serotonin level is inversely proportional to serum histamine levels with human males having 52% more serotonin than females. Data appears to show an association between the dates of violent acts from mentally ill individuals and the dates of dramatic decreases in pollen levels thus indicating a possible precursor or triggering relationship. This knowledge could be used as a potential predictor for law enforcement and medical agencies for a given city. Mental health professionals would be advised to lower serotonin boosting meds and antihistamines and even supplement sedative medications to male patients in the timeframes of mid-March to the end of June, for spring tree pollen - especially juniper, and from mid-September to the end of November, for fall pollen - primarily ragweed.