Most true food allergies are caused by proteins in food. The immune system mistakes a specific protein, called an allergen, as harmful and may trigger symptoms affecting the skin, digestion, breathing or circulation.
Not every reaction after eating is an allergy. If your child has had a suspected food reaction, a GP can review the food, timing and symptoms and discuss whether further assessment or referral may be appropriate.
Key Takeaways
- Most true food allergies are triggered by proteins found in food
- The protein causing the reaction is called an allergen
- Food allergy is different from food intolerance and additive reactions
- A positive allergy test does not confirm allergy on its own
- Anaphylaxis is a medical emergency requiring immediate treatment and a call to 000
What Component of Food Usually Causes an Allergic Reaction?
In most true food allergies, the immune system reacts to a specific protein in food. That protein is the allergen. The ASCIA food allergy guide identifies common foods associated with allergic reactions in Australia, noting that almost any food can cause allergy, though certain foods are more commonly involved.
Foods whose proteins are more commonly associated with allergic reactions include:
- Cow’s milk
- Egg
- Peanut and tree nuts
- Sesame
- Soy and wheat
- Fish and shellfish
Almost any food can trigger an allergy, but these are among the most frequently identified triggers in Australian children and adults.
Why Can a Food Protein Cause an Allergic Reaction?
The immune system may mistakenly treat a food protein as harmful and react when the food is eaten again. Many immediate reactions involve IgE antibodies, while other immune pathways can cause delayed symptoms.
Can Sugar, Fat or Food Additives Cause an Allergic Reaction?
Proteins cause most true food allergies. Lactose intolerance is a digestive reaction to milk sugar, not an allergy to milk protein. Additives and food chemicals, including sulphites, may cause other adverse reactions, while rare exceptions include alpha-gal allergy following certain tick bites.
What Is the Difference Between Food Allergy and Food Intolerance?
These terms are often used interchangeably, but they involve different processes. Understanding the difference helps guide the right clinical approach.
| Feature | Food allergy | Food intolerance |
| Main mechanism | Immune-system reaction | Usually a digestive or chemical mechanism |
| Typical trigger | Often a food protein | May involve lactose, food chemicals, or additives |
| Possible symptoms | Hives, swelling, vomiting, breathing symptoms | Bloating, gas, abdominal discomfort, or diarrhoea |
| Anaphylaxis risk | Food allergy — possible | Food intolerance — not expected |
Note that vomiting and abdominal symptoms can also occur in allergic reactions. The timing, pattern, and broader symptom picture help guide assessment.
If symptoms repeatedly occur after the same food, a general medicine consultation can help review the food, timing, and reaction pattern and discuss whether further assessment may be appropriate.
What Symptoms Can a Food Allergy Cause?
Food-allergy symptoms can range from mild to severe. Many IgE-mediated reactions begin within minutes to a couple of hours after eating the food. Symptoms may include:
- Hives, welts, or skin itching
- Swelling of the lips, face, or eyes
- Tingling or itching in the mouth
- Vomiting or abdominal pain
- Coughing, wheezing, or breathing difficulty
- Throat or tongue swelling
- Dizziness, collapse, or a pale, floppy appearance in a young child
No single symptom confirms food allergy on its own. The combination, timing, and pattern of symptoms are all important for clinical assessment.
When Is a Food Reaction an Emergency?
Anaphylaxis is a medical emergency. Signs may include difficult or noisy breathing, tongue or throat swelling, persistent coughing or wheezing, trouble speaking, dizziness or collapse.
If suspected, use the person’s prescribed adrenaline autoinjector, follow their ASCIA Action Plan and call 000 immediately. Do not wait for symptoms to improve.
How Does a GP Assess a Possible Food Allergy?
Assessment begins with the reaction history, not a test. During a general medicine consultation, a GP may ask about:
- Which food and ingredients were eaten
- How much was consumed
- How quickly symptoms began after eating
- Which symptoms occurred and how long they lasted
- Whether the same reaction has happened before
- Whether the patient has eczema, asthma, or other allergic conditions
- What treatment was used and whether it helped
Depending on the history, a GP may consider targeted allergen-specific IgE blood testing or referral to a specialist. If a GP orders a targeted blood test, ask reception whether the sample can be collected through the practice’s on-site pathology service.
Two important cautions apply. A positive skin-prick or blood test can show sensitisation but does not always confirm clinical allergy. Commercial IgG panels, hair analysis, and broad food sensitivity tests are not recommended tools for diagnosing food allergy.
What Should You Record Before the GP Appointment?
Coming prepared helps the GP build a clearer picture. Consider bringing or noting:
- The food eaten and, if possible, the full ingredient list or packaging
- The time the food was eaten and when symptoms started
- Which symptoms occurred and how long they lasted
- Photographs of visible symptoms such as hives or swelling
- Any medicines or first aid used and whether they helped
Do not deliberately reintroduce a suspected food trigger at home to confirm the reaction.
Conclusion
Most true food allergies are reactions to food proteins and are different from food intolerance. Because symptoms and test results need clinical context, a GP can review a suspected reaction and discuss whether further assessment is appropriate.
To discuss a suspected food reaction in Paterson, contact Paterson Healthcare to book a GP appointment for an initial assessment.
FAQs
What component of food usually causes an allergic reaction?
Most true food allergies are caused by proteins. The immune system mistakenly identifies a particular food protein, known as an allergen, as harmful and triggers a reaction.
Can food additives cause an allergic reaction?
Some additives, including sulphites, can cause adverse reactions in susceptible people. These are not always the same as a typical protein-triggered food allergy and require proper clinical assessment.
Is food allergy the same as food intolerance?
No. Food allergy involves the immune system and can sometimes cause anaphylaxis. Food intolerance usually involves digestive or chemical mechanisms and does not typically cause anaphylaxis.
Can a blood test confirm a food allergy?
Not by itself. A positive allergen-specific IgE result may show sensitisation, but the result must be interpreted alongside the reaction history and clinical assessment.
Should I remove the suspected food from my child’s diet?
Do not remove several foods or major food groups without GP and dietitian guidance. Unnecessary restriction can affect nutrition and growth. Seek medical advice before making significant dietary changes.
Resources and References
- ASCIA — Food Allergy
https://www.allergy.org.au/patients/food-allergy - Healthdirect Australia — Food Allergies
https://www.healthdirect.gov.au/food-allergies - ASCIA — Food Allergy Testing
https://www.allergy.org.au/patients/allergy-testing/food-allergy - Healthdirect Australia — Anaphylaxis
https://www.healthdirect.gov.au/anaphylaxis
This article provides general health information only and does not replace individual medical advice. Food-allergy symptoms, testing and management depend on the food involved, reaction history, age and individual clinical circumstances. Call 000 if someone shows signs of anaphylaxis.