Allergies stem from specific, accurate reactions of the human immune system against – usually harmless – substances of the environment or sometimes against drugs or endogenous elements (autoimmune diseases). In case of specific antibodies (humoral immune system), the reaction quickly appears within minutes or even seconds (hives, hay fever, asthma) while reactions induced by lymphocytes (cellular immune system) show after a few hours or days.
Allergies are often directed against the following substances:
- Pollen, animal hair and dust mites
- Bee and wasp venom
- Chemical substances of the environment (e.g. contact allergy against nickel)
- Food products
Not all incompatibilities are based on allergic reactions of the immune system; constitutional hypersensitivities (intolerance), e.g. to pain medication, are also not uncommon. Allergies can nowadays be accurately analysed and can often be mitigated or completely suppressed through an efficacy-specific desensitisation treatment (e.g. for pollen or insect venom).