An allergic reaction is an immune system response that fails upon recognizing an innocuous element as harmful, activating an allergy. Genes and the environment can be triggers.
For the general population, allergens are harmless substances, but in people who have allergies, their bodies recognize them as foreign or dangerous. It is common for allergies to develop over time in response to elements that are found in the environment, some of which are very common and others that are difficult to detect. Typical symptoms include coughing, sneezing, itching, skin rashes, abdominal pain and diarrhea, however these depend on the part of the body that comes into contact with the allergen.
6 groups of allergens are considered to be the most common according to the WHO: pollen, mites, mold, animal dander, food and medicine.
Keeping them under control
While there is no cure for allergies, the most effective solution to preventing them is to identify the type of allergen that is triggering the allergy early on and avoid contact with it as much as possible. In order to diagnose an allergy, skin or blood tests can be taken to identify specific antibodies. Treatment includes using medications that reduce symptoms or, in some cases, vaccines or immunotherapy.
The immune system is responsible for identifying what belongs to the body and protecting it from anything that is foreign. When people with sensitivities are exposed to allergens, their immune systems produce antibodies (immunoglobulins E), which activate the production of histamine, a protein that causes symptoms, and in some cases, anaphylactic shock (difficulty breathing). If anaphylactic shock is not treated on time, it can cause death.
10% of the population suffers from some type of allergy, some of which do not develop until later on in life.
Sources: U.S. National Library of Medicine and U.S. Food and Drug Administration.
See also: What causes respiratory allergies?