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UrticariaAPPROACH

ALLERGY AND DERMATOLOGY · 19 SECTIONS

⚲

462 items

☷ Legend

⚲

Resuscitation and Universal Approaches9▾

Chest and Cardiovascular12▾

Respiratory11▾

Abdominal and Gastrointestinal24▾

Renal and Urinary7▾

Neurologic11▾

Back and Neck8▾

Women's Health, Pregnancy, and GU11▾

Infectious Disease and Fever Syndromes11▾

Allergy and Dermatology7▾

Pruritus Without Rash Contact Dermatitis And Eczema Flare Herpes Zoster Concern Drug Eruption Concern And Severe Cutaneous Reaction Red Flags Urticaria Angioedema Concern Unexplained Bruising Or Bleeding Symptoms

Musculoskeletal and Extremities14▾

Trauma and Wounds14▾

ENT, Eye, Dental10▾

Endocrine, Metabolic, and Abnormal Labs9▾

Toxicology and Behavioral14▾

Pediatrics16▾

Environmental and Exposure4▾

01History/hx71

Presenting pattern

›Symptom characterization

›Wheals

›Transient lesions

›Migratory lesions

›Angioedema

›Lips

›Tongue

›Periorbital

›Duration classification

›Acute urticaria less than 6 weeks (L50.9)

›Chronic urticaria 6 weeks or longer (L50.8)

›Episode pattern

›Continuous daily or near daily

›Intermittent episodic

OPQRST

›OPQRST framework

›Use for time course and triggers

›Use for severity and systemic involvement

Onset

›Onset details

›Time of first lesion

›Time from exposure to rash

›First ever episode vs recurrent

Provocation/Palliation

›Trigger and relief pattern

›Medication exposures

›NSAIDs

02Alarm Features/alarm31

Immediate life threats

›High risk presentations

›Anaphylaxis (T78.2)

›Hypotension

›Respiratory compromise

›Upper airway angioedema

›Tongue swelling

›Voice change

›Drooling

›Severe asthma exacerbation triggered by allergy

›Silent chest

›Fatigue or altered mental status

Vital sign danger thresholds

›Danger thresholds

›Systolic blood pressure less than 90 mmHg or age adjusted low

›Oxygen saturation less than 92 percent on room air

›Respiratory rate 30 per minute or higher with distress

›Altered mental status

High risk exam findings

›High risk findings

›Stridor

›Immediate airway planning

›Immediate epinephrine if anaphylaxis suspected

›Rapidly progressive facial or tongue edema

›Immediate airway planning

›Early anesthesia or ENT support

›Purpura or bruising with urticarial lesions

›Urticarial vasculitis concern

03Medications/meds26

Current and recent exposures

›Medication and substance review

›New prescription medication within 6 weeks

›Recent dose increase within 2 weeks

›OTC exposures

›NSAIDs

›Cold and flu preparations

›Supplements and herbals

›New supplement within 6 weeks

›High dose biotin affecting labs

High risk medication classes

›Common urticaria and angioedema triggers

›NSAIDs

›Urticaria exacerbation in chronic spontaneous urticaria

›Bronchospasm risk in aspirin sensitive asthma

›ACE inhibitor

›Bradykinin mediated angioedema risk

›Poor response to antihistamines expected

›Opioids

›Non IgE histamine release

›Pruritus and flushing mimic

Contraindications and interaction traps

›Therapy safety considerations

›Sedating antihistamines

›Fall risk in older adults

›Driving impairment risk

›QT prolongation risk medications

›Hydroxyzine higher risk settings

04Diet/diet10

Food and exposure context

›Exposure patterns

›New food exposure within 4 hours

›Known food allergy exposure

›Alcohol exposure

›Vasodilation and symptom amplification

›Co factor for food dependent exercise anaphylaxis

Hydration and intake

›Intake context

›Poor oral intake

›Vomiting limiting oral meds

›Dehydration contributing to hypotension concern

05Review of Systems/ros22

System based screen

›ROS clusters

›Skin

›Urticaria

›Bruising or purpura

›ENT

›Throat tightness

›Hoarseness

›Pulmonary

›Wheeze

›Cough

›Cardiovascular

›Syncope or presyncope

›Lightheadedness

›Gastrointestinal

›Abdominal pain

›Vomiting

›Musculoskeletal

›Arthralgia

›Myalgia

›Endocrine

›Heat intolerance

›Cold intolerance

06Collateral History and Family History/chafh14

Source and reliability

›Collateral and context

›Witnessed exposure history

›Timing reliability

›Prior allergy testing records

Family history

›Inherited and atopic conditions

›Hereditary angioedema (D84.1)

›Family members with recurrent swelling

›Family members with abdominal attacks

›Atopy

›Asthma (J45.909)

›Allergic rhinitis (J30.9)

›Autoimmune disease

›Autoimmune thyroid disease (E06.3)

›Systemic lupus erythematosus (M32.9)

07Risk Factors/rf17

Patient specific risks

›Comorbidity risks

›Asthma severity

›Higher risk severe anaphylaxis

›Lower reserve with bronchospasm

›Cardiovascular disease

›Higher risk epinephrine adverse effects

›Lower tolerance of hypotension

›Pregnancy

›Airway edema risk

›Medication risk benefit considerations

Exposure risks

›Exposure and setting

›Recent infection exposure

›Recent vaccination

›Hymenoptera exposure risk

Medication related risks

›Bradykinin angioedema risks

›ACE inhibitor use

›ARB related angioedema history

08Differential Diagnosis/ddx33

Life threatening

›Cannot miss diagnoses

›Anaphylaxis (T78.2)

›Urticaria plus respiratory compromise

›Urticaria plus hypotension or syncope

›Angioedema with airway compromise

›Tongue or laryngeal edema

›Rapid progression over minutes

›Meningococcemia (A39.0)

›Fever with petechiae or purpura

›Toxic appearance

Common

›Common etiologies

›Acute spontaneous urticaria (L50.9)

›Often infection associated

›Often no trigger identified

›Drug associated urticaria (L50.0)

›Temporal relationship to new medication

›Improvement after discontinuation

›Physical inducible urticaria (L50.8)

›Dermatographism

›Cold urticaria

Less common

›Less common etiologies and mimics

›Chronic spontaneous urticaria (L50.8)

›Daily or near daily wheals for 6 weeks or longer

›Autoimmune association

›Urticarial vasculitis (L95.8)

09Past Medical History/pmh13

Relevant conditions

›Baseline conditions

›Prior anaphylaxis episodes

›Trigger known

›Epinephrine autoinjector access

›Chronic urticaria history

›Prior response to antihistamines

›Prior need for omalizumab

›Angioedema history

›ACE inhibitor associated episodes

›Family history suggesting hereditary angioedema

Procedures and hospitalizations

›Prior care utilization

›Prior ED visits for allergic reactions

›Prior ICU admission for airway compromise

10Physical Exam/exam33

General and vitals

›Initial assessment

›Vital sign pattern

›Hypotension

›Tachycardia

›Appearance

›Toxic appearance

›Respiratory distress

Skin

›Skin findings

›Urticarial wheals

›Blanching

›Raised edematous plaques

›Lesion duration clues

›Individual lesion less than 24 hours

›Fixed lesions 24 hours or longer

›Mimic clues

›Target lesions suggesting erythema multiforme

›Non blanching petechiae or purpura

Airway and ENT

›Upper airway evaluation

›Lip and tongue swelling

›Uvula edema

›Voice change

›Drooling or inability to handle secretions

Pulmonary

›Respiratory findings

›Wheeze

11Lab Studies/labs30

No routine labs for uncomplicated acute urticaria

›Minimal testing strategy

›No labs for isolated urticaria with stable vitals

›Targeted labs for systemic features or chronic course

Anaphylaxis and severe reaction evaluation

›Severe reaction labs

›Serum tryptase

›Useful if drawn within 1 to 3 hours of symptom onset

›Baseline repeat 24 hours later for comparison

›Basic metabolic panel

›Electrolytes and renal function for shock and fluids

›Glucose for altered mental status

Chronic urticaria targeted workup

›Chronic course labs

›CBC with differential

›Eosinophilia suggesting parasitic or drug reaction

›Neutrophilia suggesting infection or inflammation

›ESR or CRP

›Elevated values supporting vasculitis or systemic disease

›Normal values supporting uncomplicated chronic spontaneous urticaria

›TSH with reflex free T4

›Autoimmune thyroid association

›Treatment rarely resolves urticaria alone

›Liver enzymes

›Baseline prior to advanced therapies

›Hepatitis association screening context

Angioedema complement evaluation

›Bradykinin mediated angioedema labs

12Imaging/img24

Scoring Systems

›Criteria based tools

›NIAID FAAN anaphylaxis clinical criteria

›Acute illness with skin mucosal involvement plus respiratory compromise

›Acute illness with skin mucosal involvement plus reduced blood pressure

›WAO anaphylaxis criteria

›Acute onset illness with airway breathing circulation compromise

›Exposure plus hypotension or bronchospasm even without skin findings

MRI

›Rare indications

›Alternative diagnosis evaluation when focal neurologic symptoms present

›Avoid as routine for urticaria evaluation

›Airway and alternative diagnosis imaging

›CT neck with contrast local protocol dependent

›Consider when deep neck infection is suspected

›Consider when airway symptoms with unclear cause

›CT chest local protocol dependent

›Consider when pulmonary embolism concern dominates

›Not for routine urticaria

Ultrasound

›Targeted ultrasound use

›Soft tissue ultrasound

›Abscess vs cellulitis when swelling is focal

›Not for diffuse urticaria

›Abdominal ultrasound

›Consider in recurrent abdominal attacks with hereditary angioedema history

›Rule out alternative abdominal pathology

13Special Tests/spec14

Bedside and procedural diagnostics

›Targeted tests by phenotype

›Dermatographism provocation

›Linear wheal after stroking skin

›Supports physical inducible urticaria

›Cold stimulation test

›Ice cube test positive wheal

›Anaphylaxis risk with cold water immersion history

›Skin biopsy for suspected urticarial vasculitis

›Lesions lasting 24 hours or longer

›Purpura or residual hyperpigmentation

Airway evaluation

›Airway confirmation tools

›Flexible nasolaryngoscopy local protocol dependent

›Suspected laryngeal edema

›Persistent voice change or stridor

14ECG/ecg8

Indications in urticaria presentations

›ECG triggers

›Chest pain or palpitations during reaction

›Older patient receiving epinephrine

›Known cardiovascular disease with anaphylaxis

High risk patterns

›ECG red flags

›Ischemic ST changes

›Ventricular tachyarrhythmia

›Prolonged QT interval in high risk medication settings

15Assessment/ax20

Phenotype and severity stratification

›Working problem list

›Isolated urticaria without systemic features

›Stable vitals

›No respiratory or cardiovascular symptoms

›Urticaria with angioedema

›Mucosal involvement present

›Airway risk stratified by symptoms

›Anaphylaxis suspected (T78.2)

›Skin symptoms plus respiratory compromise

›Skin symptoms plus hypotension or syncope

Etiology hypothesis

›Likely trigger category

›Idiopathic or infection associated

›No clear exposure

›Viral prodrome present

›Medication associated

›Temporal relationship to exposure

›Reproducible with re exposure history

›Physical inducible

›Reproducible stimulus

›Limited distribution pattern

16Plan/plan65

First 5 minutes for critical patient

›Immediate stabilization workflow

›Monitoring

›Cardiac monitor

›Pulse oximetry

›Access

›Two IV lines for hypotension or anaphylaxis

›Intraosseous access if no IV access in shock

›Oxygen

›Supplemental oxygen for oxygen saturation less than 92 percent

›Early airway planning for stridor or voice change

›Epinephrine for anaphylaxis

›Adult epinephrine IM 0.3 mg to 0.5 mg of 1 mg per mL into lateral thigh

›Repeat every 5 to 15 minutes if persistent symptoms

Differential Management

›!Urticaria (acute)→›!Anaphylaxis→›Angioedema→

Pharmacologic ladder for isolated urticaria

›Symptom control

›Second generation H1 antihistamine first line

›Cetirizine 10 mg PO daily

›Fexofenadine 180 mg PO daily

›Up dosing for persistent symptoms off label

›Cetirizine 20 mg PO twice daily maximum 40 mg per day

›Fexofenadine 180 mg PO twice daily maximum 360 mg per day

›Sedating H1 antihistamine adjunct

›Diphenhydramine 25 mg to 50 mg PO or IV every 6 hours as needed

17Disposition/dispo16

Level of care criteria

›ICU criteria

›Persistent hypotension after fluids and repeated epinephrine

›Need for epinephrine infusion local protocol dependent

›Airway intervention or impending airway compromise

›Inpatient admission criteria

›Progressive angioedema without secured airway

›Significant comorbidity with moderate reaction

›Unreliable follow up or unsafe home setting

›Observation pathway criteria

›Anaphylaxis treated with epinephrine

›Need for multiple epinephrine doses

›Severe asthma history

›Discharge criteria

›Stable vitals for an appropriate observation period

›No progression of angioedema

›Patient understands return precautions and has medications

18Discharge Instructions/di9

Copy discharge instructions

›Discharge text

›You were treated for hives with or without swelling

›Take your antihistamine as directed for the next several days

›Avoid any suspected trigger and avoid NSAIDs if they worsened symptoms

›If you were given an epinephrine autoinjector carry it with you at all times

›Use epinephrine right away if you develop trouble breathing, throat tightness, fainting, or repeated vomiting

›Return to the emergency department now for trouble breathing, voice change, swelling of tongue, fainting, chest pain, or symptoms coming back after improvement

›Follow up with your primary care clinician within 2 to 3 days

›Allergy specialist referral within 2 to 6 weeks for recurrent episodes or unclear triggers

19References/r6

Guidelines and key sources

›Evidence based sources

›EAACI GA2LEN EDF WAO guideline for urticaria 2021 update

›AAAAI ACAAI practice parameter update for the diagnosis and management of acute and chronic urticaria 2014

›World Allergy Organization anaphylaxis guidance 2020 update

›NIAID FAAN anaphylaxis clinical criteria 2006

›ACE inhibitor associated angioedema reviews and society guidance local protocol dependent

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed February 24, 2026

SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.

UrticariaAPPROACH

ALLERGY AND DERMATOLOGY · 19 SECTIONS

⚲

462 items

☷ Legend

⚲

Resuscitation and Universal Approaches9▾

Chest and Cardiovascular12▾

Respiratory11▾

Abdominal and Gastrointestinal24▾

Renal and Urinary7▾

Neurologic11▾

Back and Neck8▾

Women's Health, Pregnancy, and GU11▾

Infectious Disease and Fever Syndromes11▾

Allergy and Dermatology7▾

Musculoskeletal and Extremities14▾

Trauma and Wounds14▾

ENT, Eye, Dental10▾

Endocrine, Metabolic, and Abnormal Labs9▾

Toxicology and Behavioral14▾

Pediatrics16▾

Environmental and Exposure4▾

01History/hx71

Presenting pattern

›Symptom characterization

›Wheals

›Transient lesions

›Migratory lesions

›Angioedema

›Lips

›Tongue

›Periorbital

›Duration classification

›Acute urticaria less than 6 weeks (L50.9)

›Chronic urticaria 6 weeks or longer (L50.8)

›Episode pattern

›Continuous daily or near daily

›Intermittent episodic

OPQRST

›OPQRST framework

›Use for time course and triggers

›Use for severity and systemic involvement

Onset

›Onset details

›Time of first lesion

›Time from exposure to rash

›First ever episode vs recurrent

Provocation/Palliation

›Trigger and relief pattern

›Medication exposures

›NSAIDs

02Alarm Features/alarm31

Immediate life threats

›High risk presentations

›Anaphylaxis (T78.2)

›Hypotension

›Respiratory compromise

›Upper airway angioedema

›Tongue swelling

›Voice change

›Drooling

›Severe asthma exacerbation triggered by allergy

›Silent chest

›Fatigue or altered mental status

Vital sign danger thresholds

›Danger thresholds

›Systolic blood pressure less than 90 mmHg or age adjusted low

›Oxygen saturation less than 92 percent on room air

›Respiratory rate 30 per minute or higher with distress

›Altered mental status

High risk exam findings

›High risk findings

›Stridor

›Immediate airway planning

›Immediate epinephrine if anaphylaxis suspected

›Rapidly progressive facial or tongue edema

›Immediate airway planning

›Early anesthesia or ENT support

›Purpura or bruising with urticarial lesions

›Urticarial vasculitis concern

03Medications/meds26

Current and recent exposures

›Medication and substance review

›New prescription medication within 6 weeks

›Recent dose increase within 2 weeks

›OTC exposures

›NSAIDs

›Cold and flu preparations

›Supplements and herbals

›New supplement within 6 weeks

›High dose biotin affecting labs

High risk medication classes

›Common urticaria and angioedema triggers

›NSAIDs

›Urticaria exacerbation in chronic spontaneous urticaria

›Bronchospasm risk in aspirin sensitive asthma

›ACE inhibitor

›Bradykinin mediated angioedema risk

›Poor response to antihistamines expected

›Opioids

›Non IgE histamine release

›Pruritus and flushing mimic

Contraindications and interaction traps

›Therapy safety considerations

›Sedating antihistamines

›Fall risk in older adults

›Driving impairment risk

›QT prolongation risk medications

›Hydroxyzine higher risk settings

04Diet/diet10

Food and exposure context

›Exposure patterns

›New food exposure within 4 hours

›Known food allergy exposure

›Alcohol exposure

›Vasodilation and symptom amplification

›Co factor for food dependent exercise anaphylaxis

Hydration and intake

›Intake context

›Poor oral intake

›Vomiting limiting oral meds

›Dehydration contributing to hypotension concern

05Review of Systems/ros22

System based screen

›ROS clusters

›Skin

›Urticaria

›Bruising or purpura

›ENT

›Throat tightness

›Hoarseness

›Pulmonary

›Wheeze

›Cough

›Cardiovascular

›Syncope or presyncope

›Lightheadedness

›Gastrointestinal

›Abdominal pain

›Vomiting

›Musculoskeletal

›Arthralgia

›Myalgia

›Endocrine

›Heat intolerance

›Cold intolerance

06Collateral History and Family History/chafh14

Source and reliability

›Collateral and context

›Witnessed exposure history

›Timing reliability

›Prior allergy testing records

Family history

›Inherited and atopic conditions

›Hereditary angioedema (D84.1)

›Family members with recurrent swelling

›Family members with abdominal attacks

›Atopy

›Asthma (J45.909)

›Allergic rhinitis (J30.9)

›Autoimmune disease

›Autoimmune thyroid disease (E06.3)

›Systemic lupus erythematosus (M32.9)

07Risk Factors/rf17

Patient specific risks

›Comorbidity risks

›Asthma severity

›Higher risk severe anaphylaxis

›Lower reserve with bronchospasm

›Cardiovascular disease

›Higher risk epinephrine adverse effects

›Lower tolerance of hypotension

›Pregnancy

›Airway edema risk

›Medication risk benefit considerations

Exposure risks

›Exposure and setting

›Recent infection exposure

›Recent vaccination

›Hymenoptera exposure risk

Medication related risks

›Bradykinin angioedema risks

›ACE inhibitor use

›ARB related angioedema history

08Differential Diagnosis/ddx33

Life threatening

›Cannot miss diagnoses

›Anaphylaxis (T78.2)

›Urticaria plus respiratory compromise

›Urticaria plus hypotension or syncope

›Angioedema with airway compromise

›Tongue or laryngeal edema

›Rapid progression over minutes

›Meningococcemia (A39.0)

›Fever with petechiae or purpura

›Toxic appearance

Common

›Common etiologies

›Acute spontaneous urticaria (L50.9)

›Often infection associated

›Often no trigger identified

›Drug associated urticaria (L50.0)

›Temporal relationship to new medication

›Improvement after discontinuation

›Physical inducible urticaria (L50.8)

›Dermatographism

›Cold urticaria

Less common

›Less common etiologies and mimics

›Chronic spontaneous urticaria (L50.8)

›Daily or near daily wheals for 6 weeks or longer

›Autoimmune association

›Urticarial vasculitis (L95.8)

09Past Medical History/pmh13

Relevant conditions

›Baseline conditions

›Prior anaphylaxis episodes

›Trigger known

›Epinephrine autoinjector access

›Chronic urticaria history

›Prior response to antihistamines

›Prior need for omalizumab

›Angioedema history

›ACE inhibitor associated episodes

›Family history suggesting hereditary angioedema

Procedures and hospitalizations

›Prior care utilization

›Prior ED visits for allergic reactions

›Prior ICU admission for airway compromise

10Physical Exam/exam33

General and vitals

›Initial assessment

›Vital sign pattern

›Hypotension

›Tachycardia

›Appearance

›Toxic appearance

›Respiratory distress

Skin

›Skin findings

›Urticarial wheals

›Blanching

›Raised edematous plaques

›Lesion duration clues

›Individual lesion less than 24 hours

›Fixed lesions 24 hours or longer

›Mimic clues

›Target lesions suggesting erythema multiforme

›Non blanching petechiae or purpura

Airway and ENT

›Upper airway evaluation

›Lip and tongue swelling

›Uvula edema

›Voice change

›Drooling or inability to handle secretions

Pulmonary

›Respiratory findings

›Wheeze

11Lab Studies/labs30

No routine labs for uncomplicated acute urticaria

›Minimal testing strategy

›No labs for isolated urticaria with stable vitals

›Targeted labs for systemic features or chronic course

Anaphylaxis and severe reaction evaluation

›Severe reaction labs

›Serum tryptase

›Useful if drawn within 1 to 3 hours of symptom onset

›Baseline repeat 24 hours later for comparison

›Basic metabolic panel

›Electrolytes and renal function for shock and fluids

›Glucose for altered mental status

Chronic urticaria targeted workup

›Chronic course labs

›CBC with differential

›Eosinophilia suggesting parasitic or drug reaction

›Neutrophilia suggesting infection or inflammation

›ESR or CRP

›Elevated values supporting vasculitis or systemic disease

›Normal values supporting uncomplicated chronic spontaneous urticaria

›TSH with reflex free T4

›Autoimmune thyroid association

›Treatment rarely resolves urticaria alone

›Liver enzymes

›Baseline prior to advanced therapies

›Hepatitis association screening context

Angioedema complement evaluation

›Bradykinin mediated angioedema labs

12Imaging/img24

Scoring Systems

›Criteria based tools

›NIAID FAAN anaphylaxis clinical criteria

›Acute illness with skin mucosal involvement plus respiratory compromise

›Acute illness with skin mucosal involvement plus reduced blood pressure

›WAO anaphylaxis criteria

›Acute onset illness with airway breathing circulation compromise

›Exposure plus hypotension or bronchospasm even without skin findings

MRI

›Rare indications

›Alternative diagnosis evaluation when focal neurologic symptoms present

›Avoid as routine for urticaria evaluation

›Airway and alternative diagnosis imaging

›CT neck with contrast local protocol dependent

›Consider when deep neck infection is suspected

›Consider when airway symptoms with unclear cause

›CT chest local protocol dependent

›Consider when pulmonary embolism concern dominates

›Not for routine urticaria

Ultrasound

›Targeted ultrasound use

›Soft tissue ultrasound

›Abscess vs cellulitis when swelling is focal

›Not for diffuse urticaria

›Abdominal ultrasound

›Consider in recurrent abdominal attacks with hereditary angioedema history

›Rule out alternative abdominal pathology

13Special Tests/spec14

Bedside and procedural diagnostics

›Targeted tests by phenotype

›Dermatographism provocation

›Linear wheal after stroking skin

›Supports physical inducible urticaria

›Cold stimulation test

›Ice cube test positive wheal

›Anaphylaxis risk with cold water immersion history

›Skin biopsy for suspected urticarial vasculitis

›Lesions lasting 24 hours or longer

›Purpura or residual hyperpigmentation

Airway evaluation

›Airway confirmation tools

›Flexible nasolaryngoscopy local protocol dependent

›Suspected laryngeal edema

›Persistent voice change or stridor

14ECG/ecg8

Indications in urticaria presentations

›ECG triggers

›Chest pain or palpitations during reaction

›Older patient receiving epinephrine

›Known cardiovascular disease with anaphylaxis

High risk patterns

›ECG red flags

›Ischemic ST changes

›Ventricular tachyarrhythmia

›Prolonged QT interval in high risk medication settings

15Assessment/ax20

Phenotype and severity stratification

›Working problem list

›Isolated urticaria without systemic features

›Stable vitals

›No respiratory or cardiovascular symptoms

›Urticaria with angioedema

›Mucosal involvement present

›Airway risk stratified by symptoms

›Anaphylaxis suspected (T78.2)

›Skin symptoms plus respiratory compromise

›Skin symptoms plus hypotension or syncope

Etiology hypothesis

›Likely trigger category

›Idiopathic or infection associated

›No clear exposure

›Viral prodrome present

›Medication associated

›Temporal relationship to exposure

›Reproducible with re exposure history

›Physical inducible

›Reproducible stimulus

›Limited distribution pattern

16Plan/plan65

First 5 minutes for critical patient

›Immediate stabilization workflow

›Monitoring

›Cardiac monitor

›Pulse oximetry

›Access

›Two IV lines for hypotension or anaphylaxis

›Intraosseous access if no IV access in shock

›Oxygen

›Supplemental oxygen for oxygen saturation less than 92 percent

›Early airway planning for stridor or voice change

›Epinephrine for anaphylaxis

›Adult epinephrine IM 0.3 mg to 0.5 mg of 1 mg per mL into lateral thigh

›Repeat every 5 to 15 minutes if persistent symptoms

Differential Management

›!Urticaria (acute)→›!Anaphylaxis→›Angioedema→

Pharmacologic ladder for isolated urticaria

›Symptom control

›Second generation H1 antihistamine first line

›Cetirizine 10 mg PO daily

›Fexofenadine 180 mg PO daily

›Up dosing for persistent symptoms off label

›Cetirizine 20 mg PO twice daily maximum 40 mg per day

›Fexofenadine 180 mg PO twice daily maximum 360 mg per day

›Sedating H1 antihistamine adjunct

›Diphenhydramine 25 mg to 50 mg PO or IV every 6 hours as needed

17Disposition/dispo16

Level of care criteria

›ICU criteria

›Persistent hypotension after fluids and repeated epinephrine

›Need for epinephrine infusion local protocol dependent

›Airway intervention or impending airway compromise

›Inpatient admission criteria

›Progressive angioedema without secured airway

›Significant comorbidity with moderate reaction

›Unreliable follow up or unsafe home setting

›Observation pathway criteria

›Anaphylaxis treated with epinephrine

›Need for multiple epinephrine doses

›Severe asthma history

›Discharge criteria

›Stable vitals for an appropriate observation period

›No progression of angioedema

›Patient understands return precautions and has medications

18Discharge Instructions/di9

Copy discharge instructions

›Discharge text

›You were treated for hives with or without swelling

›Take your antihistamine as directed for the next several days

›Avoid any suspected trigger and avoid NSAIDs if they worsened symptoms

›If you were given an epinephrine autoinjector carry it with you at all times

›Use epinephrine right away if you develop trouble breathing, throat tightness, fainting, or repeated vomiting

›Return to the emergency department now for trouble breathing, voice change, swelling of tongue, fainting, chest pain, or symptoms coming back after improvement

›Follow up with your primary care clinician within 2 to 3 days

›Allergy specialist referral within 2 to 6 weeks for recurrent episodes or unclear triggers

19References/r6

Guidelines and key sources

›Evidence based sources

›EAACI GA2LEN EDF WAO guideline for urticaria 2021 update

›AAAAI ACAAI practice parameter update for the diagnosis and management of acute and chronic urticaria 2014

›World Allergy Organization anaphylaxis guidance 2020 update

›NIAID FAAN anaphylaxis clinical criteria 2006

›ACE inhibitor associated angioedema reviews and society guidance local protocol dependent

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed February 24, 2026

SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.