This paper aims to explain the mechanism of Type 1 hypersensitivity and the corresponding action of loratadine and sodium cromoglycate. Type 1 hypersensitivity is the most common type of allergy, which is caused by mast cells and leukocytes releasing chemical mediators, including histamines, cytokines, etc. Chemical mediators cause inflammatory responses, as well as bind to receptors that generate symptoms of allergies. Coping with the reaction, loratadine is a type of antihistamine that can inhibit the activation of the H1 receptor by histamines, it is a drug that performs inverse agonism. Whereas, sodium cromoglycate stabilizes mast cells and prevents the degranulation of chemical mediators, in order to stop inflammatory responses or activation of receptors. It is a drug that behaves as a mediator. There will be explanations in regard to the chemical synthesis of loratadine and sodium cromoglycate. The paper will also touch on the dosage, mode of delivery, as well as side effects of these drugs.