Oral manifestations of systematic disease are signs and symptoms of disease occurring elsewhere in the body detected in the oral cavity and oral secretions. High blood sugar can be detected by sampling saliva. Saliva sampling may be a non-invasive way to detect changes in the gut microbiome and changes in systemic disease. Another example is tertiary syphilis, where changes to teeth can occur. Syphilis infection can be associated with longitudinal furrows of the tongue.