A 2016 systematic review identified 2 RCTs that examined whether early introduction of peanuts affects subsequent allergies.1 The first RCT recruited 1303 3-month-old infants from the general population in the United Kingdom.2 All patients had either a negative skin prick test (SPT) to peanuts or a negative oral peanut challenge (if an initial SPT was positive). The control group breastfed exclusively until age 6 months, at which time allergenic foods could be introduced at parental discretion.
Timing doesn’t affect peanut allergy in nonallergic patients
The intervention group received 6 common allergenic foods (peanuts, eggs, cow’s milk, wheat, sesame, and whitefish) twice weekly between ages 3 and 6 months. Researchers then performed double-blinded, placebo-controlled oral food challenges at ages 12 and 36 months.
More patients in the late-introduction group demonstrated peanut allergies by age 36 months than in the early-introduction group, but the difference wasn’t significant (2.5% vs 1.2%; P = 0.11).A key weakness of the study was combining peanuts with other common food allergens.2
Children with eczema, egg allergy benefit from earlier peanut introduction
The second RCT divided 640 infants with severe eczema, egg allergy, or both into 2 groups according to their response to an SPT to peanuts: patients with no wheal and patients with a positive wheal measuring 1 to 4 mm.3 Researchers then randomized patients to either early exposure (peanut products given from ages 4 to 11 months) or avoidance (no peanuts until age 60 months). The primary endpoint was a positive clinical response to oral peanut allergen at age 60 months.
In the negative SPT group (atopic children expected to have a lower risk for allergy), patients introduced to peanuts later had a higher rate of subsequent allergy than children exposed earlier (14% vs 2%; absolute risk reduction [ARR] = 12%; 95% confidence interval [CI], 3%-20%; number needed to treat [NNT] = 9).3
In the positive SPT group (atopic children expected to have a higher risk for allergy), later peanut introduction likewise increased risk compared to earlier introduction (35% vs 11%; ARR = 24%; 95% CI, 5%-43%; NNT = 5). Children in the early-exposure group, however, had more URIs, viral exanthems, gastroenteritis, urticaria, and conjunctivitis (4527 events in the early-exposure group vs 4287 in the avoidance group, P = 0.02; about 1 more event per patient over the course of the study).3
The authors of the systematic review performed a meta-analysis of the 2 RCTs (1793 patients). They concluded that early introduction of peanuts to an infant’s diet (between ages 3 and 11 months) decreased the risk for eventual peanut allergy (relative risk [RR] = 0.29; 95% CI, 0.11-0.74), compared with introduction at or after age 1 year.1 A key weakness, however, was the researchers’ choice to combine trials with very different inclusion criteria (infants with severe eczema and a general population).
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