The invention is directed to a method of detecting a biological substance in the nasal secretion and diagnosing a disease following the detection of the biological substance wherein the biological substance is not related to a respiratory disease. The invention also provides treatment of the diseases following the detection of the biological substance and/or diagnosis of the disease. In some embodiments, the diseases are cancer, hepatitis, smell loss, taste loss, diabetes, and leprosy. The invention also provides a kit for diagnosing a disease.The present invention includes methods of analyzing samples from the nose for the detection of biological substances. In particular, nasal secretion or nasal mucus is collected and analyzed for biological substances. The results of this analysis are then suitable for use in diagnosis, prognosis, and determination of suitability of therapeutic interventions.