Allergies are one of the most common consultations seen in family medicine. They effect people of all ages and can range from a mild bout of hay fever to a severe anaphylactic reaction.
Allergic reactions are caused by our own immune system inappropriately attacking a substance that it recognises as harmful (allergens). Common allergens include dust mite, milk protein, eggs, pollen and nuts. The most common allergic responses can be categorized as Type 1 and Type 2 reactions as they are mediated through two different immune pathways.
ABOUT ALLERGY REACTIONS
Type 1 Reactions usually happen within minutes of exposure to an allergen. IgE antibodies order the release of a cascade of chemicals such as histamine causing inflammation in the skin, gut and respiratory system. Typical Type 1 symptoms include:
Itchy rash & hives
Lip & facial swelling
Sneezing, runny nose and watering eyes
Abdominal pain, nausea and vomiting
Wheeze, cough, hoarseness and difficulty breathing
Low blood pressure and shock
Type 2 Reactions happen over a period of days after exposure to an allergen and are controlled by IgG antibodies. They also cause a combination or skin and gut symptoms however they are not life threatening. It can be difficult to pin point the exact allergens responsible for type 2 allergic reactions given the time delay in symptom onset. Typical Type 2 symptoms include:
Abdominal cramps, bloating, diarrhoea and constipation
Progressive vomiting and food aversion in infants
The most important part of diagnosing an allergy is the story. The first step is to establish whether an allergy is Type 1 or Type 2. A detailed symptom diary will help your doctor establish the type of reaction and the most likely culprit. Record foods, drinks, cosmetics, detergents, air fresheners, cleaning products and any work related substances that may be causing a reaction.
Cow’s milk, hen’s egg, peanut, tree-nut and fish count for over 90% of food allergies. They generally present within the first 3 years of life. People do not usually develop allergies to foods that they have previously tolerated.
Blood tests to check for IgE antibodies to specific allergens can help to confirm the diagnosis. There are, as yet, no medically approved tests available to detect for IgG Antibody reactions. In fact, as children grow and become tolerant of foods such as dairy, their IgG Antibodies will often remain elevated; similarly chicken pox antibodies are detectable years after the rash has faded. Removing dairy from their diet would deprive them of an excellent source of calcium for growing bones.
If someone is suspected of having a Type 2 reaction it is more appropriate to carefully exclude and reintroduce suspected allergens under medical guidance; such as cutting out dairy for two weeks and restarting if there is no benefit.