Acute vs. Chronic Urticaria

While the lifetime prevalence for CSU estimates range from 0.6% to 1.8% (Gaig et al., 2004; Zuberbier et al., 2010), the lifetime prevalence for acute urticaria is thought to be as high as 20% (Zuberbier et al., 2018). Furthermore, acute urticaria accounts for 7–35% of dermatological conditions seen in emergency care (Barniol et al., 2017).

Acute urticaria is defined as the occurrence of spontaneous hives, angioedema, or both for <6 weeks (Zuberbier et al., 2018).

Acute urticaria aetiology

The underlying causes of acute urticaria remain idiopathic in 50% of cases, with infections responsible for approximately 40%, and adverse reactions to drugs (9%) and food (1%) responsible for the remaining 10% of cases (Kathuria, 2011).

Managing acute urticaria

For patients with an identifiable trigger, for example a food allergy, patients should be investigated to confirm sensitisation enabling avoidance of the trigger and prevention of future episodes. With acute urticaria being time-limited, treatment is usually focused on symptomatic relief with second-generation H1-antihistamines (Zuberbier et al., 2018). In a recent study of 100 acute urticaria patients presenting at a French emergency department, 79% of patients treated with levocetirizine were itch free after two days (Barniol et al., 2017).

Current guidelines also state that a short course of oral corticosteroids (up to 10 days) may help reduce the duration and activity of acute exacerbations of urticaria (Zuberbier et al., 2018). Interestingly, in the above study, addition of prednisone to levocetirizine treatment did not improve the symptomatic or clinical response compared with levocetirizine plus placebo. This suggests that the addition of a corticosteroid to antihistamine therapy may be unnecessary in acute urticaria patients (Barniol et al., 2017).

Sensitisation to insect bites, such as mosquitos, is common and results in immediate hives and pruritic bite papules, although systemic anaphylactic reactions can also occur (Karppinen et al., 2012). Mosquito-bite hives are a result of antisaliva IgE antibodies and histamine release meaning oral second-generation H1-antihistamines can be an effective option for management of the hives and itch. Placebo-controlled trials have shown cetirizine, ebastine and rupatadine to be effective treatment options in mosquito-bite allergic adult patients. Prophylactically administered rupatadine 10 mg resulted in a 48% decrease in mean hive size and a 21% reduction in itch in these patients. Importantly, for a condition characterised by intense pruritus, rupatadine 10 mg was observed to have a rapid onset of action with a significant reduction versus placebo in hive size and itch reported 15 minutes after administration (Karppinen et al., 2012). In a separate study, prophylactic cetirizine 10 mg and ebastine 10 mg, but not loratadine 10 mg, resulted in a significant reduction in hive size. While cetirizine had a significantly greater effect on itch than ebastine and loratadine, it also increased the levels of sedation observed, although the clinical significance was uncertain as no patients dropped out (Karppinen et al., 2002).