As awareness of pet allergies continues to grow, so too does the demand for affordable, accurate and accessible diagnostic tools that quickly identify allergen sensitisation profiles and triggers. Knowing the cause enables the development of effective management strategies.
What are allergens?
Allergens are generally defined as substances capable of stimulating a mild to severe immune-associated allergic response in an exposed individual. Different types of immunoglobulins, known as antibodies, can be associated with this process. It is IgE that is primarily responsible for triggering allergic responses.
Degranulation of mast cells releases histamine and cytokines, which trigger allergic reactive symptoms.
Like humans, animals can become sensitised to a range of allergens, such as dust mites, grass and tree pollens, moulds, fleas, animal dander and food components, impacting their health, wellbeing and performance. Why this occurs is complex and is not solely linked to an individual’s genetic makeup, but can also be influenced by the environment and other factors.
Why is there an uptick in pet allergies?
As with humans, pets are increasingly suffering from allergenic responses, likely due to similar causes and as a result of modern life:
- Clean living, with limited exposure at a young age to a broad environmental and gut microbial profile.[1]
- Increased potency of airborne allergens when bound with urban pollutant carriers, which exacerbate the allergenic trigger and immune response.[2][3][4]
- Better diagnosis through awareness and testing.
Diagnosing allergy
Traditionally, diagnostic evaluation of an allergic response has been limited to a veterinary practice setting, with animals exposed to intradermal allergen testing (IDAT) and/or by taking blood samples to test for allergen-specific IgE responses.
Both approaches have well-established clinical roles, although each has advantages and limitations. IDAT requires the injection of a defined panel of allergens into the skin of the animal, and the reaction is later assessed for an allergy-induced response. However, there is potential for a severe allergic response, and the animal may need to be sedated and carefully monitored.
Requiring a small volume of blood, allergen-specific IgE screening is considered less invasive and avoids the risk of inducing an allergic response.
With an increasingly available repertoire of recombinant molecular allergen epitopes, along with native and purified allergen extracts, allergen IgE testing has become a popular diagnostic approach.
In testing, two different strategies are taken: either a bottom-up approach, evaluating an expansive panel of allergenic reagents, or a top-down approach, focusing on the main primary allergen candidates.
Some aspects to be aware of with allergen-specific IgE screening are:
- An immune response to molecular allergen components can provide a different profile response from that generated against native allergens.[5]
- The detection of an allergen-specific IgE response is indicative of sensitisation rather than a confirmed allergy.
- The generation of an extensive IgE sensitisation profile requires considerable expertise to interpret.
- IgE screening can be expensive, and a standard service can take up to a week to provide results.[6]
- With a short half-life of IgE in the serum of approximately two to three days, test results will be affected by when the sample is taken in relation to when the animal was exposed to a potential allergen.[7]
Could at-home testing be the answer?
With a top-down approach, there is a real opportunity for at-home testing using lateral flow tests (LFTs). This would enable pet owners to screen animals against common allergens such as pollen, dust mites, fungal moulds and major food allergens within a timeframe better suited to understanding allergenic triggers.
While LFTs have been developed and made commercially available for human allergen-specific IgE responses, availability for animals is markedly limited to a few tests that detect total IgE rather than an allergen-specific IgE response.
What is the barrier to at-home pet allergy testing?
Determining allergenic triggers is key to managing an allergy. Diagnosing allergies in pets can be a complex process.
- Veterinary specialist knowledge is key to a comprehensive evaluation and, if required, the development of a plan to manage the allergy.
- To detect an allergen-specific IgE response, blood samples are generally evaluated using laboratory processes such as enzyme-linked immunosorbent assay (ELISA). These tests require skilled staff and expensive laboratory equipment. With a relatively slow turnaround compared with a 10-minute rapid LFT, they will likely require visits and consultation time with a vet.
Translation of the ELISA assay to a rapid LFT format has not been widely considered, mainly due to concerns that LFTs are not as sensitive as ELISA and lack the capability to test for multiple allergens at scale.
In addition, producing a quantitative response may require a reader with inbuilt reference standards to measure an allergen-specific IgE response.
While these factors may have been true at the turn of the century, LFT technology has moved on at pace. These limitations should no longer be seen as a barrier to the vet or pet owner.
Harnessing lateral flow technology to enable affordable and accessible allergy testing in 10 minutes
Traditionally, ELISA was considered to be in the region of 10-fold more sensitive than antibody-based lateral flow. However, with technological advances, this is no longer reported to be the case.[8]
While not limited to these areas, key improvements that have enabled lateral flow to challenge this thinking include:
- Improvements in lateral flow architecture and the materials used
- Antibody and nanobody engineering
- Selection of antibodies based on the ability to measure antibody-binding kinetics
- Conjugation and labelling amplifiers
- Improved assay choreography
- Reader technology
Similarly, once thought of as a single-analyte test with a qualitative output, lateral flow technology has progressed to enable multiplex testing with quantitative outputs.[9]
References
- Farm living: effects on childhood asthma and allergy | Nature Reviews Immunology
- Current Allergy and Asthma Reports
- Environmental Pollution
- Immunological Reviews
- World Allergy Organization Journal
- How pet allergy testing works | Dragon Lab
- The half-life of IgE in serum | Journal of Allergy and Clinical Immunology
- Advances in lateral flow technology | ACS Nano
- AX-2X-S lateral flow reader | Axxin