The etiology of tumors is complex and influenced by multiple factors, including the host and environmental conditions. Allergy is primarily driven by the immune response of helper T cell 2 (Th2). Research has shown that the Th2 immune response is closely related to tumors, which is specifically manifested through Th2 antibodies, allergy-related effector cells and mediators within the tumors, as well as tumor immune-related functions. This internal interaction mechanism will increase the complexity and challenges associated with the clinical diagnosis and treatment of tumors and allergy. The formation of allergic constitution is shaped by both congenital and acquired factors, and its physical state is closely linked to the occurrence and progression of allergic diseases. Therefore, this paper aims to explore the relationship between tumors and allergic reactions from the perspective of traditional Chinese medicine (TCM) constitution theory. Based on the four basic principles of the TCM constitution, including endowment inheritance theory, environment constraint theory, body-spirit composition theory, and life process theory, this exploration will focus on four aspects: genetic factors and internal disease causes, inflammatory environments and functional regulation, psychological disorders and emotional pathogenesis, as well as age structure and disease risk. Furthermore, from the perspective of constitution-disease relation of chronic disease prevention, this paper will discuss the significant importance of adjusting allergic constitution to improve both subjective symptoms and objective indicators of allergic reactions in tumor patients.