Atypical Acquired cold urticaria (ACU) is a type of physical urticaria caused
by the release of mast cell mediators which lead to inflammation following exposure to cold. The underlying causes of ACU remain to be clarified in detail, a wide range of
diseases are associated with ACU.
Systemic cold urticaria (generalized urticaria occurring upon exposure to cold) was first reported in 1984. This form of Atypical Cold Urticaria is characterized by reactions that occur on multiple areas of the body, not just the area exposed to the cold (localized). Symptoms are difficult to control and the Cold Stimulation Timed Test (CSTT) (aka; Ice Cube Test) is always negative.
What sets this condition apart from Reflex Cold Urticaria is that reactions do occur at site exposure as well as other areas. RCU reactions do not occur at site of exposure, but other areas of the body.
Cold Induced Urticaria
Cholinergic Urticaria (ChU) is commonly triggered by heat, exercise and/or sweat. A more rare form is triggered by cold. The difference between this condition and Cold Urticaria is that Cold Induced has an appearance where the wheals are very small, pinpoint size. They are intensely itchy. The CSTT test will be negative.
The mechanism by which the cold stimulus is transformed into a signal for molecular and cellular activation has not been elucidated. Anti-IgE antibodies may play a role.
Identification of a new physically induced urticaria: cold-induced cholinergic urticaria
Cold-Induced Cholinergic Urticaria – A Case Report
A Case of Combined Cholinergic and Cold Urticaria
Evaluation of a patient with Cold and Cholinergic Urticaria
Reflex CU presents with small weals in the vicinity but not at the place of contact with cold. The lesions occurred only on the extremities and during the cold season.
Localized Cold Reflex Urticaria.
Cold Dependent Dermographism/Dermatographism
Dermatographism that is observable only upon chilling the skin subsequent to scratching it. The reaction can be associated with detectable elevation of venous histamine levels coincident with the development of urticaria.
An alternative presentation involves generalized urticaria that is induced by systemic rather than local cold challenge. The reaction can be anaphylactoid in nature and associated with systemic elevation of histamine levels.
Delayed Cold Induced Urticaria
Delayed cold urticaria may appear several hours after contact with the cold.