Pathophysiology
- Mast cell degranulation: Histamine release causes vasodilation, increased vascular permeability, and sensory nerve stimulation (pruritus)
- Type I hypersensitivity (allergic): IgE-mediated mast cell activation in response to specific allergen
- Non-immunological triggers: Direct mast cell activation by physical stimuli, medications, or complement
- Dermatographism: Wheals along lines of pressure or scratching (~5% of population)
- Chronic urticaria: Often autoimmune (IgG autoantibodies against IgE receptor on mast cells)
- Angioedema: Deeper dermal/subcutaneous swelling. When involving throat/tongue = medical emergency
Signs and Symptoms
Hallmark Indicators
- Wheals: Raised, erythematous, edematous plaques with pale centers. Variable size
- Intensely pruritic. Individual wheals transient (<24 hours)
- Wheals blanch with pressure (distinguishes from purpura, which does not blanch)
- Dermatographism: Linear wheals where skin is stroked or scratched
- Angioedema: Swelling of lips, eyelids, hands, feet. May involve tongue/throat
- No scarring, crusting, or vesicles (distinguishes from eczema, contact dermatitis)
Red Flags and Rule-Outs
- Angioedema involving throat or tongue: Medical emergency — airway compromise
- Widespread wheals with systemic symptoms (fever, joint pain): Reschedule and refer
- Wheals that do NOT blanch: Consider purpura, not urticaria — different pathology
- Distinguish from contact dermatitis (persistent, at contact site) — urticaria is transient and migratory
MT Considerations
- Active urticaria: Proceed with caution — mast cells are in heightened reactivity state
- Dermatographism risk: Massage pressure may trigger new wheals. Use light pressure and observe response
- Lubricant caution: Perform patch test with new lubricant. Fragrance-free, hypoallergenic preferred
- Widespread or severe: If widespread wheals, systemic symptoms, or any angioedema — reschedule and refer
- Stress reduction benefit: Gentle relaxation massage may help reduce stress-triggered chronic urticaria
- Latex awareness: If latex is a trigger, ensure latex-free environment
- Post-antihistamine drowsiness: Clients may be drowsy. Ensure safe departure
CMTO Exam Relevance
- Mast cell degranulation and histamine release — Type I hypersensitivity
- Wheals are transient (<24 hours), pruritic, blanch with pressure
- Angioedema involving throat/tongue is a medical emergency
- Dermatographism: wheals along lines of pressure — important for massage
- Distinguish from contact dermatitis (persistent) and purpura (does not blanch)
Key Takeaways
- Urticaria is caused by mast cell degranulation and histamine release, producing transient, pruritic wheals
- Wheals are transient (<24 hours), blanch with pressure, and resolve without scarring
- Angioedema involving throat or tongue is a medical emergency
- Massage pressure can trigger dermatographism — proceed cautiously with light pressure
- Use hypoallergenic, fragrance-free lubricants and perform patch tests