Validity verdict (step 6)
approved, checked. Reconstruction: premises are that both arms received identical aggressive eczema treatment, the sole between-arm difference was heated-egg vs placebo powder, and randomization (block 4, stratified, concealed, double-blind) balanced baseline risk; conclusion is that the OFC-confirmed allergy difference isolates the causal effect of egg introduction rather than eczema/skin-barrier management. Traced step: this is standard RCT contrast logic — holding the co-intervention (eczema management, hence the transcutaneous-sensitization route) constant across arms means it cancels in the between-arm difference, and randomization removes systematic baseline imbalance, so the residual difference is attributable to the one factor that varied. The natural undercutting probe (the effect is confounded by differential skin-barrier care) is explicitly closed by the identical-treatment premise, and no alternative factor differs by arm, so no defeater survives. The one caveat the body raises — interim stopping likely inflates the point estimate — concerns effect magnitude (a strength/likelihood matter priced downstream), not the validity of the causal-isolation step, so it does not move the verdict. Author-blind: rests on the trial design, not the source.
The intervention bundled two components: stepwise heated-egg introduction and aggressive eczema control. A skeptic could attribute the allergy prevention to improved skin-barrier/eczema management (the transcutaneous-sensitization route, in which allergen exposure through inflamed skin drives sensitization) rather than to oral tolerance induction. But the placebo arm received the same aggressive eczema treatment; the only between-arm difference was heated-egg versus placebo powder. Randomization (block size 4, stratified by site and sex, allocation concealed, double-blind) balanced baseline risk. Holding eczema management constant across arms, the difference in OFC-confirmed allergy (8% vs 38%) therefore isolates the causal contribution of oral egg introduction. The far-from-threshold p (0.0001) and large absolute effect make chance implausible, though early interim stopping means the point estimate likely overstates the true effect magnitude.