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An allergy occurs when the body overreacts to an allergen or ‘trigger’ that is typically harmless to most people. Examples of include:

  • which may cause death without prompt administration of adrenaline (epinephrine). For mild allergies
  • effective treatments are available to manage or treat allergy symptoms

Symptoms depend on the allergy, but may include: vomiting (insect allergy). Do not self-diagnose.

The symptoms and signs of allergies are common to many other medical conditions

It is important to see your doctor or clinical immunology/allergy specialist for professional diagnosis, management and treatment.

A substance in the environment that can cause an allergic reaction in susceptible people is called an ‘allergen’. There are many different allergens, but they all share one thing in common – protein. Some allergens don’t contain protein to begin with, but bind with protein once inside the body to provoke the allergic reaction.

Common allergens include:

  • including prescription medications (such as penicillin)
  • over-the-counter medicines (such as aspirin)
  • herbal preparations Allergy is the result of mistaken identity. An allergen enters the body
  • is wrongly identified by the as a dangerous substance. In response
  • the immune system makes antibodies to attack the allergen

These are specific antibodies of the IgE (immunoglobulin E) class.

When an allergen is found, IgE antibodies trigger a cascade of immune system reactions, including the release of chemicals known as mast cell chemicals. These are substances that the body normally uses to destroy micro-organisms.

The most common of these is histamine

In small amounts, histamine causes itching and reddening of the local area. In large amounts, the nearby blood vessels become dilated and the area swells with accumulated fluid. The immune system’s tendency to overreact to a harmless substance is thought to be genetic.

The term ‘atopy’ describes this genetic tendency. Doctors and clinical immunology/allergy specialists describe a person who has an allergy as being ‘atopic’ – such people usually have raised levels of IgE in their blood. About allergies allergies hay fever (allergic rhinitis) asthma eczema hives (urticaria) food allergy The symptoms of allergy range from mild to severe.

The most severe type of allergic reaction is anaphylaxis Symptoms of allergies swelling of lips, face, eyes sneezing runny nose red, watery and itchy eyes wheeze or persistent cough breathing problems swelling tongue and tightness of throat headache skin rash abdominal pain ( insect allergy ) Common allergens food – such as crustaceans , eggs , fish , milk , peanuts, tree nuts (for example, almonds, cashews, pecans and walnuts), sesame and soy products plants – pollen from grasses and plants medicines insects – such as dust mites and the venom from bees, ticks, ants and wasps moulds – such as mushroom and mould spores animal dander – such as the fur and skin flakes from domestic pets such as cats and dogs chemicals – including industrial and household chemicals and chemical products such as latex rubber The immune system reaction immune system Where to get help Your GP (doctor) NURSE-ON-CALL (616) 555-0024 – for expert health information and advice (24 hours, 7 days) American Society of Clinical Immunology and Allergy (ASCIA) What is allergy? Locate a specialist Allergy & Anaphylaxis United States Dermatologist Nutrition United States (Michigann Division) (616) 555-0200 Dietitians United States 1800 812 942 Asthma United States 1800 278 462.

Key Points

  • Examples of include: , which may cause death without prompt administration of adrenaline (epinephrine)
  • For mild allergies, effective treatments are available to manage or treat allergy symptoms
  • Symptoms depend on the allergy, but may include: vomiting (insect allergy)
  • symptoms and signs of allergies are common to many other medical conditions
  • substance in the environment that can cause an allergic reaction in susceptible people is called an ‘allergen’