The human immune system is an amazing thing. That is, most of the time. Many people have no idea how the immune system works, but they benefit from it—and sometimes suffer from it—nonetheless. The immune response is how your body identifies and protects itself against bacteria, viruses, and substances that seem foreign and potentially harmful to the body.
There are a number of different immunities: innate immunity, acquired immunity, and passive immunity.
Innate immunity is the type of immunity you have when born. Innate immunity comprises of barriers that keep destructive materials from entering your body. These barriers form the initial defense in the immune response. Healthy responses include cough reflex, enzymes in tears and skin oils, mucus that traps bacteria and small particles, skin, and stomach acid.
Acquired immunity is immunity that develops by being introduced to an antigen. Your immune system then builds a defense against that specific antigen.
Passive immunity is a result of antibodies that are made in a body that is not your own. For example, an infant has passive immunity because he or she is born with antibodies that are transferred from the baby's mother. But this passive immunity doesn't last long—these antibodies fade from the baby’s immune system at between 6 and 12 months of age.
A healthy immune system defends the body from possibly damaging agents by recognizing and responding to pathogens (such as bacteria, viruses and other microorganisms), as well as antigens. Antigens are molecules on the surface of cells, fungi, viruses, or bacteria that provoke and adaptive immune response.
When an infection develops, a healthy immune system will produce agents that attack the foreign microorganisms. For instance, the immune system may produce killer T cells (a type of white blood cell) that can identify and destroy the attacking microorganism. Additionally, the immune system makes antibodies that seek the specific invading microorganism. Antibodies then attach to and render destroy them.
There are, however, immune system response that are not healthy. Unhealthy immune responses include auto-immune disorders and environmental sensitivities.
Auto-immune Disorders
Autoimmune diseases result from an atypical immune response of the body against elements and tissues normally present in the body—plainly said, the immune system attacks what is actually normal and healthy inside the body. This may be restricted to certain organs, such as autoimmune thyroiditis, or it may involve a specific type of tissue found in different parts of the body. Immunosuppression is the typical treatment for an autoimmune disorder and involves medication that reduces the immune system’s response.
Environmental Sensitivities
Environmental sensitivities involve the immune system’s negative responses to certain foods and other factors in the environment. This happens when the body cannot handle all the toxins it comes into contact with every day. In this case, the immune system functions become overactive and react to otherwise harmless substances. There are a vast array of symptoms that come with this disorder, including headache, fatigue, dizziness, nausea, congestion, itching, sneezing, sore throat, chest pain, changes in heart rhythm, breathing problems, muscle pain or stiffness, skin rash, diarrhea, bloating, gas, confusion, trouble concentrating, memory problems, and mood changes.
Some researchers also support an idea called "the hygiene hypothesis". They believe that environmental sensitivities may also be caused by a lack of childhood exposure to infectious agents, probiotics, and parasites. Living in super-clean environments (for example, spending a great deal of time indoors without pets) may leave a child's immune system uncalibrated and over-sensitive, resulting in a host of allergies to innocuous substances later on.