Environmental and food allergen profiles
In food allergy, IgE antibodies mistakenly identify normally harmless foods (such as eggs) as threats, triggering an allergic response.
The most common food allergens responsible for the majority of reactions include: milk, eggs, peanuts, tree nuts, shellfish, fish, wheat, soy, and sesame.
Peanut
Peanut allergy is one of the most common and higher-risk food allergies in Hong Kong, with symptoms typically appearing within minutes to two hours of consumption.
The storage proteins Ara h 1, Ara h 2, and Ara h 3 are classified as high-risk proteins — capable of causing anaphylaxis in severe cases, and strongly associated with more serious reactions and an elevated risk of anaphylactic shock.
Oral itching, hives, vomiting, diarrhoea
Severe: difficulty breathing, drop in blood pressure, and potentially anaphylactic shock
Cross-reactions can occur between peanuts and tree nuts, and Ara h 2 can also cross-bind with certain tree nut sensitising proteins via IgE. A positive peanut result alone is therefore insufficient — molecular testing better identifies the true risk.
Milk
Key proteins include Casein (Bos d 8), α-lactalbumin (Bos d 4), and β-lactoglobulin (Bos d 5). Bos d 8 is a heat-stable protein commonly associated with more persistent or pronounced milk allergy.
- Infants: vomiting, bloody stools, eczema, poor growth
- Children/Adults: hives, abdominal pain, asthma, anaphylaxis
Bos d 8 positive: must avoid all dairy products (including cheese, yoghurt, butter)
Cow’s milk proteins share cross-reactive overlap with goat, sheep, and other mammalian milks — so some individuals sensitive to cow’s milk may need to avoid other animal milks as well.
If you suspect a milk sensitivity, molecular-level analysis can help distinguish higher-risk casein sensitisation from lower-risk reactions that are more likely to improve over time.
Tree Nuts & Seeds
Key Molecular Allergens:
- Hazelnut：Cor a 14
- Walnut：Jug r 1
- Sesame：Ses i 1
- Cashew：Ana o 3
- Oral itching
- Hives (urticaria)
- Eczema flare-up
- Abdominal pain, diarrhoea, vomiting
- Nasal congestion, runny nose
- Wheezing, shortness of breath
Ana o 3, Cor a 14, and Jug r 1 belong to the 2S Albumin storage protein family — highly resistant to heat and digestive enzymes, retaining their allergenic activity even after cooking. Positive results are strongly associated with hives, facial swelling, breathing difficulty, severe abdominal pain, and anaphylaxis.
Tree nut allergy is typically lifelong and requires strict avoidance.
Rice
Rice is one of the most common staple foods in Hong Kong, yet a small number of people may develop IgE-mediated immediate allergic reactions to it. Rice allergy can present as skin, gastrointestinal, or respiratory symptoms, typically appearing within minutes to two hours after consumption.
Key Molecular Allergens：
- Ory s 1
- Ory s 14
- Other rice storage proteins and related allergenic molecules
- Oral itching
- Hives (urticaria)
- Eczema flare-up
- Abdominal pain, diarrhea, vomiting
- Nasal congestion, runny nose
- Wheezing, shortness of breath
Rice belongs to the grass family (Poaceae), so some patients may also develop cross-reactions to other grains or grass pollens, such as wheat, barley, and rye. If you frequently experience discomfort after eating steamed rice, rice noodles, rice crackers, or other rice-containing foods, consider further molecular IgE testing to determine whether it constitutes a true rice allergy.
Inhalant allergens are the primary cause of year-round persistent symptoms. The home may seem like a safe haven, but it harbours numerous allergens — from mould growing in bathroom corners to dust mites invisible to the naked eye in pillowcases.
The most common indoor allergens include dust mites, animal dander, mould, and cockroaches.
House Dust Mites
House dust mite is one of the most common inhalant allergens in Hong Kong, particularly associated with perennial allergic rhinitis, asthma, eczema, and nocturnal cough.
Key sensitising proteins include Der p 1, Der p 2, Der p 10, and Der p 23. Der p 1 and Der p 2 are the primary molecular markers, while Der p 10 is a tropomyosin and more prone to cross-reactive reactions.
- Oral itching
- Hives (urticaria)
- Eczema flare-up
- Abdominal pain, diarrhoea, vomiting
- Nasal congestion, runny nose
- Wheezing, shortness of breath
Did you know? Dust mites and shellfish can have allergy cross-reactivity!
Some dust mite-sensitised individuals experience oral itching or hives when eating shrimp, crab, or lobster. This is not true seafood allergy — it results from structural similarity of Tropomyosin protein.
ApexHealth ALEX3 molecular test can precisely distinguish: if Der p 10 (dust mite) is positive but shellfish-specific protein (e.g. Pen m 1) is negative, seafood can be safely consumed.
Mold Spores
Hong Kong’s humid climate allows mould spores to persist year-round, commonly found in bathrooms, air conditioners, walls, window frames, and damp corners. Mould allergy can cause rhinitis, cough, eye irritation, and asthma — some patients react immediately, others with a delayed response.
- Alternaria alternata：Normally in outdoor air and decaying vegetation
- Aspergillus fumigatus: bathrooms, air conditioners, mouldy walls
- Cladosporium herbarum: window frames, air conditioning vents
- Penicillium: Normally occur in mouldy food, damp corners
Key Molecular Allergens：
-
Alt a 1 — Key molecular allergen of Alternaria alternata
-
Asp f 1 / Asp f 2 — Common allergenic proteins of Aspergillus fumigatus
-
Cla h-related proteins — Molecular allergens associated with Cladosporium
-
Pen ch-related proteins — Molecular allergens associated with Penicillium
Mould allergy is commonly associated with inhalant allergic reactions, with symptoms ranging from allergic rhinitis and cough to eye irritation and asthma. Some patients react immediately upon exposure, while others may experience a delayed response.
For individuals with asthma or chronic allergic rhinitis, mould sensitisation may cause symptoms to flare up repeatedly — particularly during seasonal changes, humid weather, or when indoor ventilation is poor.
Cross-sensitisation between different mould species can occur, and mould sensitisation frequently presents alongside other inhalant allergens — making symptoms more complex to identify and manage.
If you experience persistent rhinitis, cough, or asthma in damp environments, IgE or molecular allergy testing is recommended to determine which specific mould spore is the true source of sensitisation.
Pet Dander
Pet allergy is one of the most prevalent inhalant allergies in Hong Kong. Cats and dogs are the most common triggers for rhinitis, eye irritation, cough, and asthma. Direct contact is not required — allergenic proteins spread via dander, saliva, and air, and even brief exposure can trigger symptoms.
- Cat: Fel d 1 (primary allergen — from saliva and sebaceous glands)
- Dog: Can f 1, Can f 5 (saliva, dander, urine)
- Sneezing and eye redness within minutes of pet contact
- Asthma patients may experience shortness of breath and chest tightness
- Skin rash on the face or arms after contact
A commonly overlooked cross-reaction: cat dander (Fel d 2, Albumin) and pork!
Some cat-allergic individuals may experience immediate oral itching when eating undercooked pork. This occurs because cat serum albumin (Fel d 2) and pork serum albumin share a similar protein structure — known clinically as Pork-Cat Syndrome. However, high-heat cooking destroys the Albumin protein, so thoroughly cooked pork is generally safe to eat.
If you suspect an allergy to cats, dogs, or other pets, molecular testing can precisely distinguish whether your reaction is a primary sensitisation, a cross-reaction, or a genuinely high-risk allergen.
Insect venom
Insect venom allergy is one of the leading causes of severe systemic allergic reactions in adults. For most people, a sting causes only local redness and pain, but in sensitised individuals, reactions can escalate rapidly — from widespread swelling to difficulty breathing, dizziness, and anaphylactic shock.
This type of allergy is a classic immediate IgE-mediated response, meaning symptoms typically appear within minutes of the sting. After the first sting sensitises the immune system, any subsequent sting triggers IgE antibodies to activate mast cells and basophils, releasing powerful inflammatory mediators. The risk of a severe reaction often increases with each subsequent sting exposure.
Key Sensitising Proteins
- Bee：Api m 1
- Wasp：Ves v 5
- Other venom proteins and related allergenic molecules
- Redness, pain, and itching at the sting site
- Expanding swelling beyond the sting area
- Hives across the body
- Swelling of the face, lips, or eyelids
- Difficulty breathing, wheezing
- Dizziness, rapid heartbeat
- Severe cases may result in anaphylactic shock
Cross-sensitisation can occur between bee and wasp venom, but the two are not identical — molecular testing therefore helps identify which venom is the true source of sensitisation.
Some patients who have reacted to venom face a higher risk with each subsequent sting. Anyone who has experienced a systemic reaction should be assessed by a healthcare professional regarding whether to carry an epinephrine auto-injector (EpiPen) at all times.