Allergy or "allergic hypersensivity"
Allergic Hypersensitivity simply put, is an adverse immune reaction to a protein (or allergen) in our environment, which is normally harmless to the non-allergic person. It may present as mild itching of the skin, tissue swelling and wheezing or even progress to full-blown anaphylaxis and death. Only a small proportion of the population exposed to an allergen will develop an allergic reaction."Non-allergic" hypersensitivity reactions are those reproducible adverse reactions that do not involve the immune system. Diarrhoea triggered by lactose (cow's milk sugar) intolerance are a good example of a non-allergic hypersensitivity (or intolerance reaction).
Allergy develops after repeated exposure to the causative allergen. Sensitisation takes place on initial exposure (a process that may take up to 6 weeks to develop) and no adverse reaction appears to occur during this sensitisation. Some time later on repeated allergen exposure, the full-blown allergic reaction will occur. The tendency some families have to develop allergic sensitisation is termed "Atopy"
During sensitisation, Immunoglobulin E (IgE) antibodies are produced by our white blood cells and on re-exposure these IgE antibodies bind the allergen and attach to Mast Cells, which release Histamine. This triggers the beginning of the Allergic Reaction, which may manifest with anything from a mild itch to anaphylaxis and death. Late phase reactions also may follow 6 to 24 hours later with Inflammation and tissue swelling.
Some people may become sensitised to an allergen and have positive allergy tests but not ever have an allergic reaction. This is called "Latent Allergy" and has no ill effects. These people go about their lives completely oblivious to the fact that they are sensitised.
Common Allergic Manifestations include Asthma, Allergic Rhinitis or Hayfever, Atopic Eczema, Contact Dermatitis, Urticaria or Hives, Food Allergy, Allergic Conjunctivitis, Wasp Venom Allergy and allergy to Medication such as Penicillin.
