Characteristics of uniphasic and biphasic anaphylaxis in infants and young toddlers: An analysis of clinical signs, predictors and management

BACKGROUND: Rates of anaphylaxis in early childhood are rising, yet there remains a paucity of data on age-specific presentations and outcomes. While prompt treatment is essential, symptoms can differ from older children. Observation after stabilization is routinely used; however, no infant and toddler-specific data guide the duration of monitoring. Identifying predictors of biphasic anaphylaxis could help guide observation times. OBJECTIVE: To characterize symptoms of anaphylaxis in infants and toddlers, analyze predictors for biphasic anaphylaxis and get more insight into required observation times in this age group. METHODS: Anaphylaxis cases aged 0-2 years presenting to a major Emergency Department (ED) were reviewed over two 5-year-periods. We analyzed clinical features, allergens, and management, comparing uniphasic and biphasic presentations. RESULTS: Of 567,595 total ED presentations aged 0-16 years, 243 cases of 0-2-year-olds (infants/toddlers) presented with anaphylaxis (72/236,217 in 2003-2007; 171/331,378 in 2013-2017). Symptoms included urticaria (85.8%), angioedema (67.8%), wheeze/persistent cough (57.7%), vomiting (42.3%) and flushing (21.8%). Symptoms unique to infants/toddlers were pallor/hypotonia (33.5%) and persistent crying (13.8%). Biphasic anaphylaxis occurred in 4.6%, was exclusively food-induced and more common among infants (p = .048). Predictors for biphasic anaphylaxis were lower systolic blood pressure (p = .011), pallor/hypotonia (p = .046), use of fluids (p < .001), and greater severity (p = .014). Timeframe for recurrence of anaphylaxis was 70-330 min. CONCLUSION: Increased awareness of age-specific symptoms is essential for timely recognition and optimal care of infant/young toddler anaphylaxis. Cardiovascular signs, fluid resuscitation, and reaction severity may help predict recurrent anaphylaxis in 0-2-year-olds and identify which patients need observation beyond 4 h versus those safe for earlier discharge.