Sometimes allergic-like symptoms may be an expression of a background disease:
In this category, we can divide the causes of allergic symptoms into two:
- Infectious factors: in example allergic reactions may occur as a manifestation of activation of the immune system (which is the system responsible for allergic reactions, among other functions). This may happen during a viral disease. In this case the symptoms subside with the end of the infectious disease.
- Abnormal activity of the immune system: Sometimes there are allergic-like reactions in the context of autoimmune diseases (in which the body attacks itself).