Urticaria - definition, pathogenesis, classification and clinical features, diagnostic tests,
differential diagnosis, associated disorders, treatment.
- Urticaria ”Hives” – group of inflammatory disorders characterized by wheal & flare type skin
reactions (urtica, erythema) & pruritus resulting from release of histamine by activated skin
mast cells. “Angioedema” is similar reaction of subcutaneous tissue resulting in swelling. OBS
urticaria refers to disease, urtica “wheal, hive” refers to primary lesion
▪ Pathogenesis: Mast Cell degranulation (activation) due to allergens, drugs or physical
stimuli (cold, friction, pressure), stress also, causes release of histamine
▪ Clinical manifestations:
▪ Hive/Wheal – basic lesion. Features:
º Central swelling surrounded by reflex erythema
º Pruritus
º Transitory nature with individual lesions 1-24h. OBS
time frame is diagnostic
▪ Acute urticaria – lasts <6weeks
▪ Chronic urticaria – lasts >6weeks
▪ Released mediators can also cause: diarrhoea,
tachycardia, respiratory problems
▪ Classification:
▪ Histology: dilated upper dermal vessels with tissue edema.
Mixed perivascular infiltrate & eosinophils are seen.
▪ Differential diagnosis: urticarial drug reactions, serum sickness, early bullous pemphigoid,
arthropod assaults (bites & stings). OBS some disorders carry “urticaria” name but are not
“urticaria disorders” (urticaria pigmentosa, urticaria vasculitis, familial cold urticaria)
- Idiopathic Urticaria – most common*.
▪ Acute urticaria – due to food, NSAIDs, infections & infestations.
▪ Therapy: nonsedating antihistamines (sedating in evening if desired). Short
course systemic GCS (prednisolone).
▪ Chronic urticaria – due to autoreactivity (autoimmune urticaria), chronic
infections, intolerance to food.
▪ Diagnostic approaches: history, labs (serum skin test, thyroid function,
ANAs), screen chronic infections (ESR, AST, H. Pylori), food intolerance test
(pseudoallergen-free diet, oral provocation test)
º Skin prick tests (SPTs) (1st line)
▪ Therapy: find trigger. Nonsedating H1 antihistamines (first line).
, - Physical Urticaria – where one specific trigger is required to induce urticaria symptoms.
▪ Dermographism “Urticaria Factitia” – development of urticarial lesions when skin is
stroked or written on.
▪ Diagnostic approaches: write on skin, reaction is read after 5-10min
& in 4-6h.
▪ Therapy: nonsedating antihistamines
▪ Cold urticaria – due to cold exposure.
▪ Diagnostic approaches: apply 4degrees ice cube or TEMPTest for
5min. Read after 10min & after 2h.
▪ Labs: cold agglutinins, cryoglobulins, cryofibrinogen, borrelia serology
▪ Differential diagnosis: familial cold urticaria, fevers & vasculitis
▪ Therapy: warn pt (jumping into cool lake can be fatal), oral antibiotics, nonsedating
antihistamines
▪ Solar urticaria – rare due to UV.
▪ Diagnostic approaches: incremental UV ↑ test
▪ Therapy: light avoidance, nonsedating antihistamines
▪ Other types: delayed pressure urticaria, heat contact urticaria, vibratory urticaria (weals
after a vibratory stimulus to the skin. Now considered as different entity from Vibratory
Angioedema)
- Other forms of urticaria – those induced by triggers other than physical
▪ Cholinergic urticaria – triggered by ↑ in body temperature (exercise, emotional stress,
passive heat exposure). OBS often combined with other forms
▪ Clinical manifestations: tiny, transient, pruritic urticarial lesions appearing in ↑ temp.
OBS skin lesions are not typical of hives so pts describe lesions as itchy rash
▪ Diagnostic approaches: physical activity or hot bath tests
▪ Therapy: antihistamine with strong cholinergic effect (Cetirizine)
▪ Contact urticaria – due to type I allergy to contact
allergens (toxins, pseudoallergens & mast cell
activators)
▪ Diagnostic approaches: prick & patch tests, read
after 20min
▪ Therapy: avoidance, nonsedating antihistamines
▪ Other forms: aquagenic urticaria, exercise-induced
urticaria/anaphylaxis.
- Associated disorders, where urticaria is key component:
▪ Muckle-Wells syndrome – urticaria, amyloidosis & deafness. Inherited
▪ Schnitzler syndrome – urticaria, angioedema & eosinophilia
▪ Wells’ syndrome – eosinophilic cellulitis with flame figures, sometimes urticaria. Often due
to arthropod assault.
differential diagnosis, associated disorders, treatment.
- Urticaria ”Hives” – group of inflammatory disorders characterized by wheal & flare type skin
reactions (urtica, erythema) & pruritus resulting from release of histamine by activated skin
mast cells. “Angioedema” is similar reaction of subcutaneous tissue resulting in swelling. OBS
urticaria refers to disease, urtica “wheal, hive” refers to primary lesion
▪ Pathogenesis: Mast Cell degranulation (activation) due to allergens, drugs or physical
stimuli (cold, friction, pressure), stress also, causes release of histamine
▪ Clinical manifestations:
▪ Hive/Wheal – basic lesion. Features:
º Central swelling surrounded by reflex erythema
º Pruritus
º Transitory nature with individual lesions 1-24h. OBS
time frame is diagnostic
▪ Acute urticaria – lasts <6weeks
▪ Chronic urticaria – lasts >6weeks
▪ Released mediators can also cause: diarrhoea,
tachycardia, respiratory problems
▪ Classification:
▪ Histology: dilated upper dermal vessels with tissue edema.
Mixed perivascular infiltrate & eosinophils are seen.
▪ Differential diagnosis: urticarial drug reactions, serum sickness, early bullous pemphigoid,
arthropod assaults (bites & stings). OBS some disorders carry “urticaria” name but are not
“urticaria disorders” (urticaria pigmentosa, urticaria vasculitis, familial cold urticaria)
- Idiopathic Urticaria – most common*.
▪ Acute urticaria – due to food, NSAIDs, infections & infestations.
▪ Therapy: nonsedating antihistamines (sedating in evening if desired). Short
course systemic GCS (prednisolone).
▪ Chronic urticaria – due to autoreactivity (autoimmune urticaria), chronic
infections, intolerance to food.
▪ Diagnostic approaches: history, labs (serum skin test, thyroid function,
ANAs), screen chronic infections (ESR, AST, H. Pylori), food intolerance test
(pseudoallergen-free diet, oral provocation test)
º Skin prick tests (SPTs) (1st line)
▪ Therapy: find trigger. Nonsedating H1 antihistamines (first line).
, - Physical Urticaria – where one specific trigger is required to induce urticaria symptoms.
▪ Dermographism “Urticaria Factitia” – development of urticarial lesions when skin is
stroked or written on.
▪ Diagnostic approaches: write on skin, reaction is read after 5-10min
& in 4-6h.
▪ Therapy: nonsedating antihistamines
▪ Cold urticaria – due to cold exposure.
▪ Diagnostic approaches: apply 4degrees ice cube or TEMPTest for
5min. Read after 10min & after 2h.
▪ Labs: cold agglutinins, cryoglobulins, cryofibrinogen, borrelia serology
▪ Differential diagnosis: familial cold urticaria, fevers & vasculitis
▪ Therapy: warn pt (jumping into cool lake can be fatal), oral antibiotics, nonsedating
antihistamines
▪ Solar urticaria – rare due to UV.
▪ Diagnostic approaches: incremental UV ↑ test
▪ Therapy: light avoidance, nonsedating antihistamines
▪ Other types: delayed pressure urticaria, heat contact urticaria, vibratory urticaria (weals
after a vibratory stimulus to the skin. Now considered as different entity from Vibratory
Angioedema)
- Other forms of urticaria – those induced by triggers other than physical
▪ Cholinergic urticaria – triggered by ↑ in body temperature (exercise, emotional stress,
passive heat exposure). OBS often combined with other forms
▪ Clinical manifestations: tiny, transient, pruritic urticarial lesions appearing in ↑ temp.
OBS skin lesions are not typical of hives so pts describe lesions as itchy rash
▪ Diagnostic approaches: physical activity or hot bath tests
▪ Therapy: antihistamine with strong cholinergic effect (Cetirizine)
▪ Contact urticaria – due to type I allergy to contact
allergens (toxins, pseudoallergens & mast cell
activators)
▪ Diagnostic approaches: prick & patch tests, read
after 20min
▪ Therapy: avoidance, nonsedating antihistamines
▪ Other forms: aquagenic urticaria, exercise-induced
urticaria/anaphylaxis.
- Associated disorders, where urticaria is key component:
▪ Muckle-Wells syndrome – urticaria, amyloidosis & deafness. Inherited
▪ Schnitzler syndrome – urticaria, angioedema & eosinophilia
▪ Wells’ syndrome – eosinophilic cellulitis with flame figures, sometimes urticaria. Often due
to arthropod assault.
