Wheat

Wheat as a Food Allergen in the Human Body

Wheat allergy is an immune system reaction to proteins found in wheat (Triticum aestivum). It is distinct from celiac disease and non-celiac gluten sensitivity, as it is a true IgE-mediated food allergy. Wheat allergy primarily affects children, but some individuals continue to have it into adulthood. Symptoms can range from mild skin reactions to severe anaphylaxis, and in some cases, wheat-dependent exercise-induced anaphylaxis (WDEIA).

How Wheat Allergy Develops in the Immune System

Initial Sensitization (Immune Priming)

• Wheat proteins (allergens) are ingested, and some remain undigested due to their resistance to gastric enzymes.
• Dendritic cells in the gut-associated lymphoid tissue (GALT) process wheat allergens and present them to naive T-helper (Th2) cells.
• Th2 cells stimulate B-cells to produce IgE antibodies specific to wheat proteins.
• IgE binds to mast cells and basophils, making them “sensitized” to wheat allergens.

Subsequent Exposure (Allergic Reaction)

• When wheat proteins re-enter the body, they bind to IgE on mast cells.
• This triggers mast cell degranulation, releasing histamine, prostaglandins, and leukotrienes.
• These inflammatory mediators cause allergic symptoms:
  • Skin: Hives, itching, eczema
  • Gastrointestinal tract: Nausea, vomiting, diarrhea
  • Respiratory tract: Wheezing, coughing, nasal congestion
  • Systemic reaction: Anaphylaxis (severe cases)

Major Wheat Allergens and Their Role in Reactions

Wheat Allergen	Protein Family	Molecular Weight	Immune Reaction	Heat Stability
Omega-5 Gliadin (Tri a 19)	Prolamins	~50 kDa	Major cause of wheat-dependent exercise-induced anaphylaxis (WDEIA)	Highly stable
Alpha-Gliadin (Tri a 21)	Prolamins	~33 kDa	Involved in celiac disease and wheat allergy	Highly stable
Beta-Gliadin	Prolamins	~45 kDa	Moderate allergenicity, linked to gluten intolerance	Stable
Gamma-Gliadin	Prolamins	~42 kDa	Moderate allergenicity, similar to beta-gliadin	Stable
Wheat Lipid Transfer Protein (Tri a 14)	LTP	~9 kDa	Cross-reacts with peach, apple, hazelnut allergens	Highly stable
Wheat Serine Protease Inhibitors (Tri a 30)	Serpins	~20 kDa	Linked to baker’s asthma and wheat allergy	Moderate
Wheat Amylase-Trypsin Inhibitors (ATIs)	Enzyme Inhibitors	~15 kDa	Triggers innate immune responses and non-celiac wheat sensitivity	Stable

• Omega-5 Gliadin (Tri a 19) is the most allergenic wheat protein, particularly in WDEIA.
• Alpha-Gliadin (Tri a 21) is more relevant in celiac disease, but it can also trigger wheat allergy.
• Wheat Lipid Transfer Protein (Tri a 14) cross-reacts with fruit and nut allergens, making it high-risk for individuals with multiple food allergies.
• Many wheat allergens are heat-stable, meaning baked or processed wheat products can still trigger allergic reactions.

Symptoms of Wheat Allergy

Mild to Moderate Reactions

• Skin: Itching, hives, eczema flares
• Gastrointestinal (GI): Nausea, vomiting, diarrhea, bloating
• Respiratory: Sneezing, runny nose, coughing, mild wheezing
• Oral Allergy Syndrome (OAS): Itchy mouth/throat after consuming wheat, particularly in those with pollen allergies.

Severe Reactions (Anaphylaxis) Requires immediate administration of epinephrine (EpiPen®).

• Airway restriction: Difficulty breathing, throat swelling
• Drop in blood pressure (anaphylactic shock)
• Dizziness, fainting, confusion
• Swelling of lips, tongue, or face
• Rapid heartbeat (tachycardia)

Wheat-Dependent Exercise-Induced Anaphylaxis (WDEIA)

• Triggered when wheat is consumed before exercise
• Results in severe allergic reactions, including anaphylaxis
• Omega-5 Gliadin (Tri a 19) is the primary culprit

Cross-Reactivity with Other Allergens

Cross-Reactive Grains (Cereal Allergies)

Cross-Reactive Allergen	Common Sources	Cross-Reactive Wheat Protein
Barley (Hordein)	Barley-based foods, beer	Omega-5 Gliadin, Beta-Gliadin
Rye (Secalin)	Rye bread, whiskey	Alpha-Gliadin
Oats (Avenin)	Oatmeal, oat flour	Moderate cross-reactivity with gliadins

Individuals with wheat allergy may react to barley, rye, and oats, especially in gluten-containing products.

Cross-Reactive Non-Cereal Foods

Cross-Reactive Allergen	Common Sources	Cross-Reactive Wheat Protein
Peach, Apple, Hazelnuts	Fruits, nuts	Wheat LTP (Tri a 14)
Grass Pollen	Airborne allergens	Wheat Proteins (Tri a 40)

Individuals with wheat allergy may also experience symptoms when exposed to grass pollen (pollen-food syndrome).

Diagnosis of Wheat Allergy

Skin Prick Test (SPT)

• Detects IgE-mediated allergic response to wheat proteins.

Serum IgE Testing

• Measures specific IgE antibodies to wheat allergens.

Oral Food Challenge

• Gold standard for confirming wheat allergy, performed under medical supervision.

Component-Resolved Diagnostics (CRD)

• Detects specific wheat allergens (Tri a 19, Tri a 14, etc.) to assess reaction severity and cross-reactivity risk.

Managing Wheat Allergy

Strict Wheat Avoidance

• Avoid all wheat-based foods:
  • Bread, pasta, crackers, baked goods
  • Processed foods with wheat starch, wheat protein isolates
  • Some cosmetic and skincare products contain wheat-derived ingredients

Alternative Grains

Wheat-Free Substitute	Safe Alternative
Wheat Flour	Rice flour, almond flour, coconut flour
Wheat Pasta	Rice pasta, lentil pasta, chickpea pasta
Wheat Bread	Gluten-free bread (made with oat, rice, sorghum, or millet)

Emergency Treatment

• Epinephrine injection (EpiPen®) for anaphylaxis.
• Antihistamines for mild allergic reactions.
• Corticosteroids for prolonged symptoms.

Conclusion

• Wheat allergy is caused by multiple proteins (Gliadins, LTPs, ATIs, Serine Protease Inhibitors).
• Omega-5 Gliadin (Tri a 19) is the most allergenic, especially in WDEIA.
• Wheat allergens are heat-stable, meaning baked products retain allergenicity.
• Cross-reactivity occurs with barley, rye, oats, and certain fruits/nuts.
• Severe wheat allergy can lead to anaphylaxis, requiring strict avoidance and emergency preparedness (EpiPen®).