Allergy

It is important in all patients to inquire about allergies and clearly document in the chart. It is also very important to clarify the manifestations of a reaction in order to diagnose a true allergic reaction versus medication intolerance or viral rash. Always re-evaluate allergy history whenever prescribing a new medication or during periodic health examinations.  True allergic reaction (anaphlyactic) is an immune IgE mediated hypersensitivity reaction.Anaphalactoid reactions are not IgE mediated but have similar symptoms. Both involve release of mast cell and basophil immune mediators.   Common allergens in ages 0-19 tend to be food related. After age of 19 insects and medications are the main allergens.

History

• Previous exposure history. First exposure causes sensitization. Re-exposure causes allergic reaction.
• Intolerance is dose dependent. Does not cause anaphlaxis
• Common allergens:
  • foods (nuts, shell fish,sulfite, milk, eggs, soy, wheat)
  • Inspect stings
  • Medications
  • Latex
  • Exercise
  • Cold
  • Contrast dye
  • Blood products
  • Idiopathic

Physical Examination

• Vitals: hypotension, tachycardia, arrhythmia
• General: anxious, tremor, increase WOB
• HEENT: lip, tongue, throat swelling, pruritic eyes, difficulty swallowing
• Resp: SOB, wheeze, stidor
• Abdo: pain, Nausea, vomit, diarrhea
• Skin: urticaria, edema, pruritis, erythema

Spectrum of IgE mediated Food Allergies

• Anaphylaxis
• Food dependent exercise induced anaphylaxis: ingest food first then exercise
• Acute urticaria
• Atopic dermatitis 35% of children with atopic dermatitis have a food allergy. Improve with removal of suspected foods
• Oral allergy syndrome: symptoms limited to mouth/throat. Local reaction to food products - mild tongue/lip swelling + pruritis. Progression to systemic symptoms is rare. 

Anaphylaxis

Diagnosis

• Rapid onset (minutes to hours) occuring after exposure to an allergen and requires either 2+ body system involvement or low blood pressure
• Body systems: skin, respiratory, GI, cardiovascular

Management

• Call for help
• Remove causative agent if possible
• ABCs + Vitals + Oxygen + Monitors + IV fluid bolus (1L NS adults, Peds 20 cc/kg NS)
• Position: supine, elevate lower extremity
• IM epinephrine (to all patients with respiratory symptoms or hypotension)
  • Adults: 0.3-0.5mg 1:1000 IM. Can repeat in 5-15 minutes
  • Pediatrics 0.01 mg/kg 1:1000. Can repeat in 5-15 minutes
  • If severe reaction can also give IV/ETT/infusion
• If on B-Blocker: glucagon 
• Diphenhydramine - adults 50mg IV, pediatrics 1mg/kg
• Ranitidine 50mg IV (adult)
• Methylprednisolone 125mg IV (adult)
• Ventolin PRN
• Monitor for delayed hypersensitivy reaction (exact time of monitoring varies in the literature)
  • provide education to patient
  • Can occur 8-72 hours post exposure
  • Can rx steroids (prednisone 50mg PO daily x 4 days)+ benadryl x 4 days to prevent
  • Return to emergency room if delayed reaction occurs
• Provide prescription for epipens x 2-4 (at all times). Instruct patient/parent on proper use. Educate on symptoms of anaphylaxis. If epipen used should proceed to ER for evaluation
  • Epipen 0.3mg IM for adults
  • Epipen Junior 0.15mg for children <25kg  
  • Epipen should be administered IM in lateral thigh
  • Epipens expire after 1 year
  • Have epipens availble in school, car, home
• Education to: Avoid allergen
• +/- Consider referral to allergist if uncertainty regarding cause
• Advise MedicAlert bracelet for anyone with an anaphylactic allergy

Anaphylaxis in Children

MIlk Protein Allergy

• Usually occurs within first year of life. Can be IgE and non-IgE mediated. Most common is cows milk protein allergy
• Clinical:
  • Usually present with symptoms of allergic reactions (as above)
  • Also have GI and nutritional manifestations. These include gastroesophageal reflux, esophagitis, gastritis, delayed gastric emptying, enteropathy, colitis, constipation, and failure to thrive.
  • +/- Behavior symptoms crying inconsolably and refusing feeding 
• Diagnosis: history alone. Confirmation requires elimination and reintroduction of the suspected allergen.
• Management: diet modification for nursing mothers and hydrolyzed formulas for formula fed infants M

Allergic Rhinitis

• Chronic respiratory illness, immunoglobulinE mediated disease thought to occur after exposure to allergens
• Allergen examples: dust, animal danders, molds, pollen, insects
• Clinical: rhinorrhea, nasal congestion, obstruction, pruritis. Symptoms tend to occur: seasonal/perennial/occupation
• DDX of rhinitis: allergic (most common), viral, vasomotor, hormonal, drug-induced, structural, irritant/occupational
• Diagnosis: based on careful history.
  • + percutaneous skin test (patch testing) if severe symptoms or unclear diagnosis or potential candidate for allergen avoidance treatment or immunotherayThe most common diagnostic tests for allergic rhinitis are the percutaneous skin test and the allergen-specific immunoglobulin E (IgE) antibody test
  • + IgE antibody test (radioallergosorbent test) if patch testing not practical/availble or are taking medications that interfere with skin testing
• Treatment:
  • Allergen avoidance
  • Mild-moderate: inhaled corticosteroids
  • Moderate to severe not responsive to intranasal steroids: antihistamines (oral, nasal spray, eye drops), decongestants (duration of use <3-5 days as can cause rebound congestion), sodium cromoglycate (nasal spray or eye drops), leukotriene receptor antagonists (montelukast -singulair; only minimal benefit), inhaled anticholinergic  (ipatropium-atroven; only effective for excessive rhinorrhea)
  • Other option: immunotherapy (consider if other methods not useful)
• If occurs during specific season = seasonal allergy /hayfever

Sick Building Syndrome

• Clinical:occupants of building experience acute or comfort related effects that are linked directly to time spent in building. Most report symptom relief soon after leaving building
• Symptoms: diffuse- can include; HA, dizziness, nausea, ear/nose/eye/throat irritation, dry cough, itching skin, trouble concentration, fatigue, sensitive odors, hoarse voice, cold, flu-like symptoms
• Etiology: chemical/biological contaminants, inadequate ventilation, electromagnetic radiation, psychological factors, poor lighting, bad acoustics, poor ergonomics, humidity
• Managmenet:
  • Prevention
  • Work place health and safety
  • Occupational Health and Safety Resource Center
  • Occupational hygienists 

Resources

http://www.cps.ca/documents/position/emergency-treatment-anaphylaxis

http://www.aafp.org/afp/2010/0615/p1440.html

http://www.cfp.ca/content/54/9/1258.full