The body can reject implants and, of course, blood if it's not your own type or O negative (I think). You can look at Allergies the same way - hay fever, nuts, strawberries - the body detects them as harmful even though they are harmless.
antigen- any substance the body regards as foreign
Antigen.
If it can be harmful, it can be referred to as pathogen.
One term that is used is antigen. An antiGEN will GENerate an ANTIbody which will 'kill' the antigen.
A foreign substance is a substance that doesn't belong somewhere. A piece of glass or splinter is a foreign substance that people get in their body.
A foreign substance is a substance that doesn't belong somewhere. A piece of glass or splinter is a foreign substance that people get in their body.
Antigen.
pathogen
An antibody is a substance formed by the body in response to a perceived foreign substance. Antibodies are produced by the immune system to help identify and neutralize potentially harmful invaders, such as bacteria and viruses.
A foreign substance circulating in the bloodstream is often referred to as a "toxin" or "foreign agent." These substances can include pollutants, pathogens, drugs, or other harmful materials that can disrupt the body's normal functioning and cause adverse effects on health. It is important for the body's immune system to identify and eliminate these foreign substances to maintain overall well-being.
Antigenan·ti·gen/ˈantijən/Noun:A toxin or other foreign substance that induces an immune response in the body, esp. the production of antibodies.
A foreign substance is any material that is not naturally present in a certain environment or body. It can come from outside sources and may cause harm, contamination, or interference with normal processes.