Course:PostgradFamilyPractice/ExamPrep/99 Priority Topics/Allergy

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Allergy - Key Features

1. In all patients, always inquire about any allergy and clearly document it in the chart. Re-evaluate this periodically.
It is important to determine both the allergen, type of reaction, when the reaction occurred and whether there has been exposure since the initial reaction without repeat reaction.

2. Clarify the manifestations of a reaction in order to try to diagnose a true allergic reaction (e.g., do not misdiagnose viral rashes as antibiotic allergy, or medication intolerance as true allergy).
Allergy Medical history food allergy.png

Intolerance vs true allergy: An allergy is IgE mediated. It happens acutely (within 20min) with every exposure and is NOT dose dependant. Allergic symptoms include: urticaria, angioedema, flushing, rhinitis, stridor, vomiting etc. Intolerance IS dose dependant and may not happen with small amounts of exposure. Patients should avoid things they are intolerant or allergic to however the distinction is vital because intolerance does NOT cause anaphylaxis.

3. In a patient reporting allergy (e.g., to food, to medications, environmental), ensure that the patient has the appropriate medication to control symptoms (e.g., antihistamines, bronchodilators, steroids, an EpiPen).
For details of treatment see point 7.

4. Prescribe an EpiPen to every patient who has a history of, or is at risk for, anaphylaxis.
EpiPen training kits can be obtained from the manufacture for patients and family members to learn how to use it. EpiPen’s expire after 1 year. For more information and resources

5. Educate appropriate patients with allergy (e.g., to food, medications, insect stings) and their families about the symptoms of anaphylaxis and the self-administration of the EpiPen, and advise them to return for immediate reassessment and treatment if those symptoms develop or if the EpiPen has been used.
An EpiPen is meant to give a patient enough time to get to an ER where they can then be fully treated and monitored for anaphylaxis. It does NOT replace emergency medical attention.

6. Advise patients with any known drug allergy or previous major allergic reaction to get a MedicAlert bracelet.

7. In a patient presenting with an anaphylactic reaction:
a) Recognize the symptoms and signs.
Anaphylaxis is defined as "a severe allergic reaction to any stimulus, having sudden onset, involving one or more body systems (oral, cutaneous, GI, cardio, resp) with multiple symptoms." The two most common manifestations of anaphylaxis are urticaria and angioedema.

Other symptoms include:
Swelling of the throat, lips, tongue
Difficulty breathing or swallowing
Metallic taste or itching in the mouth
Generalized flushing, itching, or redness of the skin
Stomach cramps, nausea, vomiting, or diarrhea
Plunging blood pressure
Sudden feeling of weakness
Anxiety or an overwhelming sense of doom

b) Treat immediately and aggressively.
Adrenaline (Epi) should be given to all patients with respiratory difficulty and hypotension
Mild Rxn:

- Diphenhydramine 50-100mg PO/IM (peds 1-2mg/kg) then q4-6h PRN +/- ranitidine IV (50mg q8h) or PO (150mg q12h) for puritis
- Epinephrine SC 0.3-0.5ml 1:1000

Mod Rxn:

- Epinephrine SC 0.3-0.5ml 1:1000 solution followed by hydrocortisone 200mg IM or slow IV. May repeat epi q5-20 min x 3 PRN
- IV, O2 by mask, Ventolin neb PRN
- ECG monitor, ABGs, lytes
- Consider for ICU for 24 hours

Severe Rxn:

- Maintain airway (consider intubation), O2 by mask, IV, foley
- If pt is in shock run 0.9% NaCl through IV wide open
- Epinephrine 1:10 000 solution (1mg/10ml) 0.5-1.0ml IV q1min up to total of 1-2mg (10-20cc) /hr. (Peds 0.01mg/kg 1/10 000 solution q5min x 1 PRN)
- IF no IV access give SL or endotracheally (use IV doses). If no response consider Dopamine at 2mcg/kg/min titrated to effect
- Solucortef 500mg IV (peds 5-10mg/kg) q6hr
- Diphenhydramine 50mg IV over 3min +/- Ranitidine 50mg IV
- Ventolin nebs PRN
- ECG monitor, ABGs, lytes
- Consider ICU admission

c) Prevent a delayed hypersensitivity reaction through observation and adequate treatment (e.g., with steroids).
Biphasic reactions are common and a patient should remain under observation at least 4 hours after being treated for anaphylaxis.

8. In patients with anaphylaxis of unclear etiology refer to an allergist for clarification of the cause.

9. In the particular case of a child with an anaphylactic reaction to food:
a) Prescribe an EpiPen for the house, car, school, and daycare.
b) Advise the family to educate the child, teachers, and caretakers about signs and symptoms of anaphylaxis, and about when and how to use the EpiPen.

10. In a patient with unexplained recurrent respiratory symptoms, include allergy (e.g., sick building syndrome, seasonal allergy) in the differential diagnosis.

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