Flare-up of allergic rhinitis has been implicated in worsening neuropsychiatric symptoms such as hyperactivity and anxiety in the general population, mostly supported by epidemiological data. However, it is unknown how such respiratory allergy symptoms affect behavioral symptoms in patients with intellectual disability and limited expressive language. These patients may express more severe behavioral symptoms partly due to frustration and anxiety, being under-diagnosed and undertreated secondary to a lack of proper communication means. Herein, we present two cases of patients with severely limited expressive language , in whom we observed marked improvement in behavioral symptoms and even cognitive activity following control of their symptoms of allergic rhinitis with the use of omalizmab, a humanized anti-IgE antibody. The presented cases indicate that clinicians need to be aware of profound effects of allergy rhinitis on neuropsychiatric symptoms in individuals with limited expressive language.