Allergy is nothing more than the immune system reacting to a generally harmless foreign substance, which is perceived as harmful by the body, such as pollen, bee venom, or pet hair (allergens). The immune system usually produces antibodies that protect the body from dangerous invaders (bacteria, virus). In case of an allergy, the immune system produces antibodies that identify a particular allergen as something harmful, even when it is not. When the immune system comes into contact with the allergen, it causes an inflammatory response which can be local or systemic, and can affect the skin, airways, eyes, etc…
This usually causes the following symptoms:
Nose: swelling of the nasal mucosa, sneezing, runny nose (allergic rhinitis).
Eyes: redness and itching of the conjunctiva (allergic conjunctivitis). It is almost always accompanied by allergic rhinitis.
Lower airways: irritation, bronchoconstriction, asthma attacks.
Skin: allergic dermatitis such as eczema, urticaria, neurodermitis (partially) and contact dermatitis.
The systemic allergic response is also called “anaphylaxis”; depending on the level of severity, it can cause skin rashes, bronchoconstriction, oedema, hypotension, up to anaphylactic shock with possible onset of coma, which can be lethal. Despite the fact that most allergies cannot be cured, different treatments can be used to help prevent and alleviate the symptoms.