Does an antigen cause allergic reaction?

No, an antigen does not directly cause an allergic reaction. An antigen is a foreign substance that triggers an immune response in the body. When the immune system encounters an antigen, it produces antibodies to neutralize it. In some cases, the immune system can overreact to an antigen, causing an allergic reaction. This occurs when the body's immune system mistakenly identifies a harmless substance as a threat and produces antibodies against it. When the person is exposed to the substance again, the antibodies bind to it and release histamine and other chemicals that cause symptoms such as sneezing, runny nose, watery eyes, and itching.