Always smell a pesticide odor may be the environment, abnormal olfactory function, mental illness and other reasons. 1. Environment: always smell a pesticide odor, may be their own place of residence around people using pesticides, such as spring plowing busy farmers use pesticides for a longer period of time; may also be their own residence around the pesticide factory or pesticide sales store, and so on. 2. Abnormal olfactory function: always smell a pesticide odor may be related to abnormal olfactory function, the body appears nasopharyngeal diseases, affecting the normal sense of smell. 3. Mental illness: always smell a pesticide odor may be caused by mental illness, such as suffering from obsessive-compulsive disorder, affected by the disease will appear olfactory hallucinations, obviously no pesticide odor but always feel that they smell pesticides. If they are not around the use of pesticides or pesticides do not exist, they always smell pesticides, need to go to the regular hospital in a timely manner.