Allergic Disorders Overview

Allergic Disorders Overview

• Twenty percent of the general population has an allergic disorder
• Family history is a strong predictor of allergies
• 30-50% of individuals have an allergic disorder if one first-degree relative has an allergic disorder
• 75% of individuals have an allergic disorder if two first-degree relatives have an allergic disorder
• Allergic disorders such as atopic dermatitis, asthma, allergic rhinitis, and food allergies often co-exist.

Objectives

• Identifying mechanisms of allergic reactions (immediate and delayed hypersensitivity)
• Differentiating food allergy from food intolerance
• Recognizing the signs, symptoms, and management of anaphylaxis
• Describing the pathophysiology of anaphylaxis
• Identifying signs and symptoms of food allergies
• Listing investigations for IgE-mediated and non-IgE-mediated food allergies
• Discussing long-term management of food allergies

Adverse Food Reactions

• Adverse reactions can be non-immune mediated (metabolic, pharmacologic, toxic) or immune mediated (IgE, non-IgE, mixed)
• IgE-mediated reactions are immediate hypersensitivity reactions
• Non-IgE-mediated reactions are delayed hypersensitivity reactions
• Examples of immune-mediated reactions: anaphylaxis, food protein-induced enterocolitis syndrome, eosinophilic esophagitis

Allergic Reaction Mechanism

• Allergen (antigen) triggers the production of IgE antibodies by B-cells
• Subsequent allergen exposure causes IgE binding to mast cells or basophils
• The binding triggers degranulation and release of histamine
• Histamine increases blood capillary permeability and distension

IgE-Mediated Food Reactions

• 6-8% of children and 3-4% of adults experience food allergies
• Detailed history is crucial (food suspected, exposure details, specific symptoms, timing, reproducibility)
• Top nine food allergens include soy, eggs, peanuts, fish, sesame, shellfish, tree nuts, milk, and wheat
• Exposure details include previous exposure or route of exposure (ingestion, contact, inhalation).

IgE-Mediated Food Reactions: Symptoms

• Cutaneous: urticaria, angioedema
• Respiratory: rhinorrhea, cough, wheeze, shortness of breath.
• Gastrointestinal: nausea, abdominal pain, vomiting, diarrhea
• Cardiovascular: fainting, hypotension

IgE-Mediated Food Reactions: Timing and Reproducibility

• Reactions typically begin within minutes to two hours of exposure
• Reactions resolve within a few hours
• Reactions are reproducible with subsequent exposures to the same food

Case Study #1 (Infant)

• Symptoms: diffuse urticaria, wheeze, stable vitals
• Trigger: cow's milk protein 15 minutes prior
• Diagnosis: anaphylaxis
• Management: discontinue cow's milk protein, epinephrine, intravenous fluids

Case Study #2 (Infant)

• Symptoms: profuse vomiting, lethargy
• Trigger: oats (3 spoonfuls)
• Diagnosis: oat-induced enterocolitis syndrome
• Management: remove oats from diet

Case Study #3 (Adolescent)

• Symptoms: diarrhea, cramping, bloating (30 minutes after eating)
• Trigger: cow's milk protein foods (tolerates smaller amounts)
• Diagnosis: suspected cow's milk protein allergy.
• Management: determine cause

Non-IgE Mediated Food Allergies

• Immunologic reaction likely T-cell mediated
• Symptoms typically limited to the gastrointestinal tract (proctitis, enterocolitis)
• Examples of non-IgE-mediated responses include food protein-induced enterocolitis syndrome, and food protein-induced proctitis

Food Protein-Induced Proctitis

• Exclusively breastfed infants (2-8 weeks old)
• Transfer of the mother's ingested foods through breast milk
• Signs include cow's milk protein, egg, soy, corn.
• Presentation: blood-tinged stools (otherwise healthy symptoms).
• Skin testing and serum-specific IgE are often unhelpful

Food Protein-Induced Enterocolitis Syndrome

• Onset 1–4 weeks after introduction of food
• Foods implicated: cow's milk protein, soy, grains, rice, meat/poultry, egg, potato, legumes
• Symptom: repetitive vomiting (1–3 hours after ingestion)
• Skin testing and serum-specific IgE are often unhelpful.

Lactose Intolerance

• Non-immune mediated food reaction
• Caused by low levels of lactase enzyme in the small intestine, causing lactose to ferment, causing abdominal pain, bloating and diarrhea
• Treatment: lactose-free products.

Skin Prick Testing

• Solutions containing proteins (food, aeroallergens, venom, medications) are placed on the skin
• If the patient is sensitized, a localized hive develops.

Serum Specific IgE

• Laboratory test detecting the presence and quantifying allergen-specific IgE to identify allergic reactions

Allergy Referral

• Patient history is the primary tool for allergic disorders.

Management

• Discontinue the allergen
• Epinephrine auto-injector
• Intravenous fluids
• Antihistamines (for hives only)
• Anaphylaxis action plan
• Medical identification devices