Gut Health · Nov 11, 2026
Food Sensitivities, Intolerances & Allergies: Know the Difference and Track Your Triggers
Confused about food reactions? Learn how to tell allergies, intolerances, and sensitivities apart, and discover how tracking your meals can help pinpoint triggers.
By Michelle Pearlman, MD, Gastroenterologist & ByteMD co-founder
If you've ever felt bloated, itchy, foggy, or fatigued after eating, you may have wondered—"Am I allergic to this?" The truth is, food reactions can come from allergies, intolerances, or sensitivities—each with different causes, symptoms, and treatments.
This blog breaks them down and shows you how to track your daily symptoms and meals to help uncover hidden food triggers.
What's the Difference?
Food Allergy
A food allergy is an immune system response. Even small amounts of the food can cause an immediate and potentially life-threatening reaction.
- Involves: IgE antibodies
- Onset: Within minutes to 2 hours
- Examples: Peanuts, shellfish, milk, eggs
- Symptoms: Hives, swelling, throat tightness, vomiting, anaphylaxis
Allergies can be fatal and require medical attention, including EpiPen® use.
Food Intolerance
A food intolerance is a digestive issue where your body can't properly break down a component in the food.
- Involves: Enzyme deficiency or chemical reaction
- Onset: Delayed—several hours after eating
- Examples: Lactose intolerance, alcohol intolerance
- Symptoms: Gas, bloating, diarrhea, cramping
Intolerances are uncomfortable but not life-threatening.
Food Sensitivity
This is a non-allergic, non-intolerance reaction to certain foods. The mechanism is not fully understood, but may involve immune activation (non-IgE) or gut-brain interaction.
- Involves: Inflammation, gut permeability, microbiome response (possible)
- Onset: Delayed—several hours to days
- Examples: Gluten (non-celiac), nightshades, additives like MSG
- Symptoms: Fatigue, brain fog, joint pain, skin issues, GI distress
Sensitivities are real but hard to diagnose without personalized tracking.
Common Symptoms to Watch For
| System Affected | Possible Symptoms |
|---|---|
| GI tract | Bloating, diarrhea, gas, constipation |
| Skin | Eczema, acne, hives, flushing |
| Neurologic | Brain fog, headache, irritability |
| Respiratory | Nasal congestion, sneezing, asthma flares |
| Musculoskeletal | Joint pain, fatigue |
Recommended Testing
| Type of Issue | Suggested Testing |
|---|---|
| Allergy | Skin prick test, blood test (IgE) |
| Intolerance | Breath tests (lactose, fructose, SIBO) |
| Sensitivity | Elimination diet + symptom tracking |
| Celiac Disease | Blood panel + biopsy (for gluten sensitivity) |
Be cautious with commercial IgG food sensitivity tests—they lack consistent accuracy and may reflect exposure, not reaction.
Use BYTEMD to Track and Identify Patterns
Daily symptom and food tracking can reveal patterns that testing alone can't. Use BYTEMD or a simple journal to log:
- What you ate (ingredients and meal timing)
- Symptoms (type, severity, timing)
- Stress, sleep, exercise
- Any supplements or medications
Sample Log: June 10, 2025
- Breakfast: Oatmeal with almond milk
- Lunch: Turkey sandwich, pickles
- Dinner: Stir-fry with tofu, bell pepper, soy sauce
- Symptoms: Bloating at 2 PM, mild headache at 6 PM
- Stress: High during work meeting
- Sleep: 6.5 hours
By logging daily for 2–4 weeks, you may find surprising correlations between foods and how you feel.
Action Plan
- Rule out food allergy with a licensed allergist
- Try elimination/reintroduction diets under guidance
- Track meals and symptoms in BYTEMD
- Bring your log to your healthcare provider or registered dietitian
Final Thoughts
Whether it's a true allergy, digestive intolerance, or delayed sensitivity, food reactions are personal—and tracking is powerful. You are your best detective when it comes to figuring out what works for your body.