Allergy is an abnormal reaction or increased sensitivity to certain substances, which are harmless to non-allergic people. The main reason for this is that allergic people make a special type of antibody called Immunoglobulin E (IgE), which can react with environmental substances in a harmful way. These substances, which lead to secretion of IgE antibodies, are called allergens.
The reaction between allergens and IgE antibodies causes the release of substances such as histamine, which produce allergic symptoms in the skin, the nose, the eyes, the chest, etc.
The most common allergens are animal danders, pollens, house dust, house mites, moulds, some drugs and many foodstuffs, especially fish, eggs, milk, and nuts. Bee and wasp stings may cause allergic reactions, with fatal results in rare cases. Additionally, feathers, wool, dyes, cosmetics, and perfumes may act as allergens.
Two main types
- Seasonal allergies like hay fever are more common in the spring when plant pollination begins. Trees and grass cause most symptoms in the spring, while ragweed is responsible for the majority of autumn symptoms.
- Perennial allergies are usually year-round problems. Common triggers for perennial allergies include mould spores, pet danders and dust mites.
- Pollens (trees, grass and weeds)
- House dust
- Dust mites
- Bee stings
- Air pollutants
Allergic reactions or diseases may involve any part of the body; the most frequently involved are the nose and chest with resultant symptoms of hay fever (rhinitis), or asthma, respectively. The skin and eyes also commonly show allergic symptoms. Anaphylactic shock is a severe allergy, which affects many organs at the same time causing a rapid decrease in blood pressure, fainting, and occasionally death. However, such a reaction is rare.
What are the risk factors?
- A personal or family history of allergies.
- Continued exposure to a known allergen. For example, if a person has a feather allergy and continues to sleep on a feather pillow, the likelihood of developing an allergis response is greater than if a foam pillow is used.