Allergies are an immune system reaction to substances that don't harm most people. This can include pollens, dust, foods, cosmetics, and such. The body produces antibodies to neutralize the foreign substance, which triggers the release of histamine, which produces what we see as allergies or Asthma. the symptoms of allergies can vary from; a runny nose, itchy eyes, itchy palate; rash, sneezing, hives and naseau.
Treatment can work on any part of the process: avoiding the allergen, reducing the production of histamines, etc. Allergies should be taken seriously; most allergic reactions are merely annoying but some can lead to sinus infections or in extreme cases they can be life threatening. Making it important for you to treat your allergies.
When the term allergy was coined, it referred to a broad category of adverse reactions to substances. Today, allergy specifically refers to an immunologic interaction between an allergen and an antibody. Other adverse reactions are now typically referred to as intolerances.
It also causes breathing to stop if it is that serious like I have.