**3.1 Epidemiology**

Evidence suggests [9] that the prevalence of CSU is geographically heterogenous, high in all groups and increasing. It is just as common in children as it is in adults [9]. Lifetime prevalence is 9% [5] with an overall point prevalence in all age groups estimated at 0.7% [4, 9]. The point prevalence is higher in women than in men (1.3% vs. 0.8%) [4, 9] but same in children (1.1% boys vs. 1% girls) [9]. CSU is more common in adolescents and the commonest subgroup of CU [2]. It has a lifetime risk of 20% [7] and is self-limiting with an average duration of 2–5 years, although in up to 30% of patients the symptoms may persist for >5 years [10].
