In 1909, Noon’s successful treatment of hay fever rhinitis with autoimmunotherapy ushered in a new era of immunotherapy. After more than half a century of practice, immunotherapy showed some clinical effectiveness, but since the 1980s, several cases of death due to injection of immunotherapy agents occurred in the UK, leading to a total ban on immunotherapy ordered by the relevant government agencies. The first successful treatment of allergic rhinitis using sublingual desensitization therapy (i.e., sublingual specific immunotherapy (SLIT)) by Scadding and Brostoff in 1986 renewed hope for immunotherapy. In 1992, the World Health Organization (WHO) confirmed the effectiveness of immunotherapy for type I allergic diseases through an evidence-based approach and concluded that “it should be applied as soon as possible if conditions are available”, and immunotherapy was reintroduced. In 1993, the European Academy of Allergic and Clinical Immunology (EAACI) pointed out that sublingual specific immunotherapy (SLIT) could be a potentially valuable treatment. In 1998, the WHO Opinion on Allergen Immunotherapy pointed out that “desensitization is the only possible cure for allergic diseases” and formally recommended the effectiveness and safety of sublingual specific immunotherapy. Currently, sublingual desensitization is being promoted in Europe and the United States, while subcutaneous immunotherapy is fading out of mainstream medical treatment due to its potential hazards. In 2001, the Global Initiative for Asthma Control (ARIA) confirmed the safety of sublingual desensitization with high doses of allergens (at least 100 times the cumulative dose of subcutaneous immunotherapy) for children and adults. In 2004, the World Health Organization endorsed SLIT as one of the main treatments for certain allergic diseases such as allergic asthma and allergic rhinitis.