Understanding Food Sensitivities
by: Dr. Paul Chang, General Practitioner, Regis Medical
Understanding Food Sensitivities
Food sensitivities, often referred to as delayed hypersensitivity reactions, are different from food allergies. Instead of an immediate immune reaction, they usually involve IgG (Immunoglobulin G) antibodies and cause subtle but chronic symptoms — such as bloating, brain fog, fatigue, and inflammation — hours or even days after consumption.
The gut plays a central role here. When certain foods cause inflammation or irritation in the digestive tract, the immune system may begin reacting to them. Over time, this can contribute to chronic conditions like IBS, eczema, migraines, and joint pain.
Now let’s dive into the top 10 most common food triggers.
Food sensitivities are often immune-mediated responses involving IgG antibodies rather than the IgE antibodies typically associated with allergies. This means that symptoms can be delayed by several hours to even days, making it hard to pinpoint the exact food causing the issue.
These sensitivities often develop due to factors like:
- Increased intestinal permeability (leaky gut)
- Gut dysbiosis (an imbalance in healthy gut bacteria)
- Overconsumption of common antigens
- Chronic stress, poor diet, and environmental toxins
- Repeated exposure to processed or inflammatory foods
The following 10 foods are among the most clinically observed triggers in IgG food sensitivity testing. Each of them can exacerbate low-grade inflammation, particularly in people already dealing with autoimmune conditions, chronic digestive issues, eczema, migraines, fatigue, or unexplained inflammation.
Dairy Products
Dairy is one of the most common food sensitivities worldwide. Unlike lactose intolerance (which is enzymatic), dairy IgG sensitivities involve an immune reaction to proteins such as casein and whey. These proteins can irritate the gut lining in sensitive individuals, especially if intestinal permeability is already compromised.
Casein, particularly A1 beta-casein found in most commercial cow’s milk, has been shown to promote pro-inflammatory cytokines in sensitive individuals. Goat and sheep’s milk may be better tolerated due to their A2 proteins, but this varies person to person.
Common symptoms triggered by Dairy
- Skin issues (acne, eczema, rosacea)
- Sinus congestion or post-nasal drip
- Gas, bloating, loose stools
- Fatigue and mood changes
Gluten (Wheat, Barley, Rye)
While celiac disease is an autoimmune condition triggered by gluten, many others suffer from non-celiac gluten sensitivity (NCGS). In these cases, gluten can increase zonulin levels, a protein that modulates tight junctions in the gut lining—leading to increased intestinal permeability.
Repeated gluten exposure in sensitive individuals can provoke low-grade inflammation, leading to systemic effects including joint pain, fatigue, and brain fog, even without overt gastrointestinal symptoms.
Common symptoms triggered by Gluten
- Abdominal bloating or discomfort
- Headaches or migraines
- Brain fog and concentration difficulties
- Skin rashes (e.g., dermatitis herpetiformis)
Eggs
Egg sensitivities can involve either the white (albumin) or yolk (lipoproteins). While highly nutritious, eggs are a top 5 IgG trigger in most sensitivity panels. Sensitivities may develop after gut infections or in individuals with dysbiosis.
Frequent consumption — especially when undercooked or raw — may increase the risk of sensitization. People with pre-existing eczema, asthma, or IBS are more prone to react to eggs.
Common symptoms triggered by Eggs
- Bloating, cramps, and indigestion
- Eczema or skin irritation
- Fatigue or mild joint aches
- Irritability or mood swings
Soy (Tofu, Soy Milk, Soy Sauce, Lecithin)
Soy contains complex proteins like glycinin and β-conglycinin, which can be difficult to digest and often trigger immune reactivity in sensitive individuals. Additionally, soy’s phytoestrogens can influence hormone balance.
Soy is heavily used in processed food products (e.g., soy oil, lecithin), making exposure frequent and cumulative. Fermented soy (tempeh, miso) is often better tolerated due to reduced allergenicity.
Common symptoms triggered by Soy
- Hormonal imbalances (PMS, acne, weight changes)
- Gut bloating, cramps
- Brain fog or energy crashes
- Skin flare-ups
Corn (Corn Syrup, Cornmeal, Corn Chips)
Corn is not only widely consumed but also present in a range of hidden forms (e.g., modified corn starch, corn syrup). It is also commonly genetically modified, which may influence immune tolerance in some individuals.
The protein zein, found in corn, is structurally similar to gluten and can cross-react in sensitive individuals. For those with leaky gut, even small exposures can trigger inflammation.
Common symptoms triggered by Corn
- Joint stiffness
- Fatigue
- Sinus congestion
- Itchy skin
Nightshades (Tomatoes, Peppers, Eggplant, Potatoes)
Nightshades contain alkaloids like solanine and capsaicin, which can stimulate the immune system and act as irritants, particularly in individuals with rheumatoid arthritis or autoimmune disease.
These compounds can increase gut permeability and may contribute to cytokine activation, worsening symptoms of chronic inflammation.
Common symptoms triggered by Nightshades
- Joint pain or flare-ups in arthritis
- Muscle aches
- Gastrointestinal symptoms like reflux or bloating
- Brain fog
Shellfish
Shellfish contains the protein tropomyosin, which can trigger both IgE allergies and IgG-mediated sensitivities. Reactions can be mild but persistently inflammatory when shellfish is consumed regularly. Cross-contamination in seafood processing and high levels of histamine in shellfish can exacerbate food sensitivities and histamine intolerance.
Common symptoms triggered by Shellfish
- Itchy skin or hives
- Abdominal cramping
- Dizziness or lightheadedness
- Chronic fatigue
Nuts (Almonds, Walnuts, Cashews, Peanuts)
Nuts are a healthy source of fats and protein, but they are also high in phytates and lectins, which can be inflammatory in sensitive individuals. Peanuts, which are legumes (not true nuts), are particularly problematic due to mold exposure and allergenic proteins.
Sensitivities may develop due to overconsumption or poor digestion — especially if nuts are eaten raw and not soaked or roasted.
Common symptoms triggered by Nuts
- Skin rashes
- GI bloating or discomfort
- Brain fog
- Migraines
Food Additives (MSG, Preservatives, Artificial Dyes)
Additives are non-nutritive chemicals that can stimulate the immune system or trigger histamine release, especially in sensitive individuals or children. MSG in particular has been shown to affect neurotransmitter activity, leading to headaches or mood issues.
Additives can alter the gut microbiome and increase intestinal permeability, amplifying sensitivity reactions over time.
Common symptoms triggered by Food Additives
- Headaches and palpitations
- Behavioural issues (especially in kids)
- Skin flushing or itching
- Digestive upset
Sugar and Refined Carbohydrates
Refined sugars promote gut dysbiosis and can feed yeast and pathogenic bacteria, leading to increased gut inflammation and permeability. Chronically high sugar intake raises insulin and inflammatory markers like CRP (C-reactive protein).
High sugar diets are linked to elevated AGEs (advanced glycation end-products) that contribute to tissue damage and systemic inflammation.
Common symptoms triggered by Sugar and Refined Carbohydrates
- Fatigue and brain fog
- Skin issues (acne, rosacea)
- Hormonal fluctuations
- Mood instability
Could Your Symptoms Be Food-Related?
If you're experiencing chronic symptoms like bloating, fatigue, skin issues, or brain fog, it's possible that one or more of these common foods are to blame. Because food sensitivity reactions can be delayed and difficult to trace, testing is often the best way forward.
At our clinic, we offer medically supervised IgG Food Sensitivity Testing to help identify your personal triggers and create a personalised plan to reduce inflammation, heal your gut, and restore your health.
Screen for Food Intolerances with Regis Medical
Comprehensive, fast result, personalised review session
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U.S. Food and Drug Administration. (n.d.). Most common food sensitivities. Verywell Health. Retrieved April 24, 2025, from https://www.verywellhealth.com/most-common-food-sensitivities-1944845
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