Rash / skin eruption EMS Clinical Reference

Clinical snapshot

Twenty-second review

A rash may arise from allergy, infection, inflammation, medication, vascular bleeding, or toxin exposure; morphology and systemic involvement determine risk.
Mucosal involvement, non-blanching lesions, skin pain, bullae, fever with toxicity, airway symptoms, shock, or rapid spread is high risk.
Keep cellulitis or vascular bruising in the differential; overlapping or concurrent illness remains possible.
For rash / skin eruption, trends and combinations of findings are more informative than one isolated vital sign.

Differentials

Compare the clinical patterns

The repeated material is grouped inside each possibility. Open only the condition you need.

Serious3 conditions

AnaphylaxisTime-sensitive high-risk possibility

HPI

Clarify onset and progression; itch, pain or blistering; mucosal involvement.

Signs & symptoms

Airway, shock, non-blanching rash, mucosal injury, or systemic toxicity.

Focused exam

Describe distribution, colour, blanching, warmth, tenderness, swelling, bullae, necrosis, and mucosal involvement; Assess systemic findings and photograph only according to consent and policy.

Brief pathophysiology

Anaphylaxis may cause rash / skin eruption through a time-sensitive process capable of rapid physiological deterioration.

Vital-sign pattern

What the trend may show

Possible pattern

Anaphylaxis may involve airway, breathing, or circulation alone or in combination. Do not wait for hypotension, hypoxemia, or skin findings before recognizing a severe reaction.

Blood pressure (mmHg)

May fall

Vasodilation and capillary leak can cause rapid hypotension.

Heart rate (bpm)

Often rises

Tachycardia may accompany shock, distress, or epinephrine treatment.

Respiratory rate (breaths/min)

Often rises

Tachypnea may reflect bronchospasm, airway edema, or shock.

Oxygen saturation (SpO₂)

May fall

Desaturation suggests significant respiratory involvement but may be late.

Front-load in the triage report

Anaphylaxis: Airway, shock, non-blanching rash, mucosal injury, or systemic toxicity.
Onset and progression?
Itch, pain or blistering?

Meningococcal diseaseTime-sensitive high-risk possibility

HPI

Clarify itch, pain or blistering; mucosal involvement; new medication or exposure.

Signs & symptoms

Airway, shock, non-blanching rash, mucosal injury, or systemic toxicity.

Focused exam

Assess systemic findings and photograph only according to consent and policy; Describe morphology and distribution, blanching, mucosa, palms and soles, skin pain, new medications, exposure, and systemic findings.

Brief pathophysiology

Meningococcal disease may cause rash / skin eruption through a time-sensitive process capable of rapid physiological deterioration.

Vital-sign pattern

What the trend may show

Possible pattern

No single vital sign diagnoses sepsis. New tachypnea, abnormal temperature, tachycardia, or falling pressure—especially with altered mentation or poor perfusion—supports organ dysfunction and urgency.

Respiratory rate (breaths/min)

May rise early

Tachypnea is included in NEWS2 and can precede overt hypotension.

Temperature (°C)

High or low

Absence of fever does not exclude sepsis; hypothermia is concerning.

Heart rate (bpm)

Often rises

Tachycardia is common but may be blunted by age or medication.

Blood pressure (mmHg)

May fall

Relative hypotension and trend matter; profound hypotension can be late.

Front-load in the triage report

Meningococcal disease: Airway, shock, non-blanching rash, mucosal injury, or systemic toxicity.
Itch, pain or blistering?
Mucosal involvement?

Severe drug reactionTime-sensitive high-risk possibility

HPI

Clarify mucosal involvement; new medication or exposure; fever or systemic symptoms.

Signs & symptoms

Airway, shock, non-blanching rash, mucosal injury, or systemic toxicity.

Focused exam

Assess systemic findings and photograph only according to consent and policy; Describe morphology and distribution, blanching, mucosa, palms and soles, skin pain, new medications, exposure, and systemic findings.

Brief pathophysiology

Severe drug reaction may cause rash / skin eruption through a time-sensitive process capable of rapid physiological deterioration.

Vital-sign pattern

What the trend may show

Possible pattern

Most skin findings do not create a specific vital-sign pattern. Temperature, heart rate, pressure, and respiratory status help identify infection, systemic allergy, toxicity, or another high-risk process.

Temperature (°C)

Trend temperature

Fever or hypothermia raises concern for infection or severe systemic illness.

Heart rate (bpm)

May rise

Tachycardia may reflect fever, pain, dehydration, or systemic involvement.

Blood pressure (mmHg)

Usually preserved

Hypotension suggests anaphylaxis, sepsis, or another shock state.

Respiratory rate (breaths/min)

Usually near baseline

Tachypnea can indicate respiratory allergy, sepsis, pain, or toxicity.

Front-load in the triage report

Severe drug reaction: Airway, shock, non-blanching rash, mucosal injury, or systemic toxicity.
Mucosal involvement?
New medication or exposure?

Common3 conditions

AllergicCommon presentation pattern

HPI

Clarify onset and progression; itch, pain or blistering; mucosal involvement.

Signs & symptoms

Itch, exposure, and preserved physiology may support a benign pattern.

Focused exam

Describe distribution, colour, blanching, warmth, tenderness, swelling, bullae, necrosis, and mucosal involvement; Assess systemic findings and photograph only according to consent and policy.

Brief pathophysiology

Allergic may explain the presenting symptoms through a common clinical mechanism, while serial assessment checks for complications or an alternate cause.

Vital-sign pattern

What the trend may show

Possible pattern

Most skin findings do not create a specific vital-sign pattern. Temperature, heart rate, pressure, and respiratory status help identify infection, systemic allergy, toxicity, or another high-risk process.

Temperature (°C)

Trend temperature

Fever or hypothermia raises concern for infection or severe systemic illness.

Heart rate (bpm)

May rise

Tachycardia may reflect fever, pain, dehydration, or systemic involvement.

Blood pressure (mmHg)

Usually preserved

Hypotension suggests anaphylaxis, sepsis, or another shock state.

Respiratory rate (breaths/min)

Usually near baseline

Tachypnea can indicate respiratory allergy, sepsis, pain, or toxicity.

Front-load in the triage report

Itch, exposure, and preserved physiology may support a benign pattern.
Onset and progression?
Itch, pain or blistering?

ViralCommon presentation pattern

HPI

Clarify itch, pain or blistering; mucosal involvement; new medication or exposure.

Signs & symptoms

Itch, exposure, and preserved physiology may support a benign pattern.

Focused exam

Assess systemic findings and photograph only according to consent and policy; Describe morphology and distribution, blanching, mucosa, palms and soles, skin pain, new medications, exposure, and systemic findings.

Brief pathophysiology

Viral may explain the presenting symptoms through a common clinical mechanism, while serial assessment checks for complications or an alternate cause.

Vital-sign pattern

What the trend may show

Possible pattern

Most skin findings do not create a specific vital-sign pattern. Temperature, heart rate, pressure, and respiratory status help identify infection, systemic allergy, toxicity, or another high-risk process.

Temperature (°C)

Trend temperature

Fever or hypothermia raises concern for infection or severe systemic illness.

Heart rate (bpm)

May rise

Tachycardia may reflect fever, pain, dehydration, or systemic involvement.

Blood pressure (mmHg)

Usually preserved

Hypotension suggests anaphylaxis, sepsis, or another shock state.

Respiratory rate (breaths/min)

Usually near baseline

Tachypnea can indicate respiratory allergy, sepsis, pain, or toxicity.

Front-load in the triage report

Itch, exposure, and preserved physiology may support a benign pattern.
Itch, pain or blistering?
Mucosal involvement?

Contact eruptionCommon presentation pattern

HPI

Clarify mucosal involvement; new medication or exposure; fever or systemic symptoms.

Signs & symptoms

Itch, exposure, and preserved physiology may support a benign pattern.

Focused exam

Assess systemic findings and photograph only according to consent and policy; Describe morphology and distribution, blanching, mucosa, palms and soles, skin pain, new medications, exposure, and systemic findings.

Brief pathophysiology

Contact eruption may explain the presenting symptoms through a common clinical mechanism, while serial assessment checks for complications or an alternate cause.

Vital-sign pattern

What the trend may show

Possible pattern

Most skin findings do not create a specific vital-sign pattern. Temperature, heart rate, pressure, and respiratory status help identify infection, systemic allergy, toxicity, or another high-risk process.

Temperature (°C)

Trend temperature

Fever or hypothermia raises concern for infection or severe systemic illness.

Heart rate (bpm)

May rise

Tachycardia may reflect fever, pain, dehydration, or systemic involvement.

Blood pressure (mmHg)

Usually preserved

Hypotension suggests anaphylaxis, sepsis, or another shock state.

Respiratory rate (breaths/min)

Usually near baseline

Tachypnea can indicate respiratory allergy, sepsis, pain, or toxicity.

Front-load in the triage report

Itch, exposure, and preserved physiology may support a benign pattern.
Mucosal involvement?
New medication or exposure?

Mimics2 conditions

CellulitisImportant alternative presentation

HPI

Clarify onset and progression; itch, pain or blistering; mucosal involvement.

Signs & symptoms

Focal warmth or non-inflammatory bleeding can mimic diffuse rash.

Focused exam

Describe distribution, colour, blanching, warmth, tenderness, swelling, bullae, necrosis, and mucosal involvement; Assess systemic findings and photograph only according to consent and policy.

Brief pathophysiology

Cellulitis can resemble rash / skin eruption through overlapping symptoms or referred physiology despite a different primary mechanism.

Vital-sign pattern

What the trend may show

Possible pattern

Most skin findings do not create a specific vital-sign pattern. Temperature, heart rate, pressure, and respiratory status help identify infection, systemic allergy, toxicity, or another high-risk process.

Temperature (°C)

Trend temperature

Fever or hypothermia raises concern for infection or severe systemic illness.

Heart rate (bpm)

May rise

Tachycardia may reflect fever, pain, dehydration, or systemic involvement.

Blood pressure (mmHg)

Usually preserved

Hypotension suggests anaphylaxis, sepsis, or another shock state.

Respiratory rate (breaths/min)

Usually near baseline

Tachypnea can indicate respiratory allergy, sepsis, pain, or toxicity.

Front-load in the triage report

Focal warmth or non-inflammatory bleeding can mimic diffuse rash.
Onset and progression?
Itch, pain or blistering?

Vascular bruisingImportant alternative presentation

HPI

Clarify itch, pain or blistering; mucosal involvement; new medication or exposure.

Signs & symptoms

Focal warmth or non-inflammatory bleeding can mimic diffuse rash.

Focused exam

Assess systemic findings and photograph only according to consent and policy; Describe morphology and distribution, blanching, mucosa, palms and soles, skin pain, new medications, exposure, and systemic findings.

Brief pathophysiology

Vascular bruising can resemble rash / skin eruption through overlapping symptoms or referred physiology despite a different primary mechanism.

Vital-sign pattern

What the trend may show

Possible pattern

Most skin findings do not create a specific vital-sign pattern. Temperature, heart rate, pressure, and respiratory status help identify infection, systemic allergy, toxicity, or another high-risk process.

Temperature (°C)

Trend temperature

Fever or hypothermia raises concern for infection or severe systemic illness.

Heart rate (bpm)

May rise

Tachycardia may reflect fever, pain, dehydration, or systemic involvement.

Blood pressure (mmHg)

Usually preserved

Hypotension suggests anaphylaxis, sepsis, or another shock state.

Respiratory rate (breaths/min)

Usually near baseline

Tachypnea can indicate respiratory allergy, sepsis, pain, or toxicity.

Front-load in the triage report

Focal warmth or non-inflammatory bleeding can mimic diffuse rash.
Itch, pain or blistering?
Mucosal involvement?

Red flags

Findings that should escalate concern

Airway swelling
Mucosal lesions
Purpura with fever
Skin sloughing
Mucosal involvement, non-blanching lesions, skin pain, bullae, fever with toxicity, airway symptoms, shock, or rapid spread is high risk.
Anaphylaxis, meningococcal disease, or severe drug reaction: Airway, shock, non-blanching rash, mucosal injury, or systemic toxicity.

Related medications

Medication recognition

Apixaban Rivaroxaban Clopidogrel Warfarin Cetirizine Epinephrine auto-injector

Continue the clinical pathway

References

Clinical and academic sources

Curated clinical guidance and peer-reviewed evidence supporting this presentation. Current BCEHS guidance, medical direction, and local policy remain authoritative for practice.