Joint occurrence of Σ28 MVOCs and absolute humidity was associated with an indication of significant interaction in additive scale on multiple allergy symptoms and asthma diagnosis. The homes with a high concentration of the purported Σ28 MVOC were not only associated with a high absolute humidity, but also were poorly ventilated. Focused strategies to remediate indoor absolute humidity and ventilation are warranted for the protection of children from allergies and asthma.