Supporting GPs in Diagnosis and Management 

In this article, Dr Steele discusses how laboratories support GPs in diagnosing allergic diseases, avoiding unnecessary requests and testing, and delivering better outcomes for patients. 

Along with autoimmune diseases, the number of allergic diseases including respiratory, food, and skin allergies are increasing around the world and affecting different population groups at different rates.  

The reason for the increasing prevalence is uncertain and there are different theories on the cause, but it is likely exposure to certain microorganisms in early childhood is crucial for building tolerance in adult life.   

While laboratory testing can identify triggers for certain allergies, it is also important GPs identify and understand the potential triggers for allergic diseases in a patient. This assessment should be driven by a patient’s history to allergies, distinguishing between immediate versus delayed reactions, along with classifying whether the reaction is immunological and non-immunological.  

Differentiating allergic reactions and intolerances by GPs 

Non-immunological reactions are more common and affect up to 30 percent of the population. These reactions can be due to intolerances to foods (e.g. gluten), pharmacologic reactions. (e.g. caffeine sensitivity), toxicity, psychological factors, and general food aversion. There are medical conditions which can mimic these reactions to foods including pancreatic insufficiency, gallstones and auriculotemporal syndrome. 

The auriculotemporal syndrome, also known as Frey’s syndrome, is characterized by sweating, flushing, and warmth over the skin in front of the ear (preauricular area) and temple in response to eating, smelling, or even thinking about food. 

Less common are immunological reactions to foods, including anaphylaxis, oral allergy syndrome and some cases of asthma can also be allergen driven.  

Clinical assessment and diagnostic approaches 

Another practical way to classify a patient’s adverse reactions to foods is distinguishing those allergies persistent from childhood, often severe and lifelong, to those occurring as an adult which have variable severity.  

Certain foods will more commonly cause allergic reactions including peanuts, tree nuts, seafoods, cow’s milk and egg. Unlike children, it is rare for adults to develop nutritional deficiencies when avoiding these foods alone unless other foods are being removed from their diet due to food intolerances and aversions.  

For some food allergies, there are other co-factors which need to be present for the reaction to occur, which can make it challenging to identify the trigger. These co-factors include menstruation, medications such as NSAIDs, exercise or concurrent infections. The presence of atopy can indicate the nature of the hidden food trigger such as storage mite anaphylaxis which occurs in atopic individuals sensitised to house dust mite.  

Oral allergy syndrome is a condition where individuals develop oral symptoms with fresh fruit and vegetables. It is due to sensitization to birch pollen cross reacting with proteins in these foods in atopic people. Testing for sensitization to birch supports the diagnosis but allergy testing to foods is not helpful when trying to identify which foods cause a reaction.  

One approach is the Lick Test where the patient licks food, waits five minutes and if there is no reaction, carefully eats it. An EpiPen is generally not needed in these cases, except for higher risk populations who had anaphylactic reactions in the past. Anti-ulcer therapy should be avoided as this can increase the risk of anaphylactic reactions.  

Optimising laboratory tests and supporting GPs 

GPs play a critical role in identifying and understanding the potential triggers for allergic diseases in a patient, diagnosing symptoms, and therefore severity of any potential reaction.  

Providing this guidance to GPs and supporting a clinical approach to allergies can avoid unnecessary requests and reduces pressures on pathology staff and resources. Optimizing patient care through better management of allergic diseases delivers cost benefits to the health system and better patient outcomes in New Zealand.   

Dr Richard Steele
Medical Director