We hypothesized that prolonged or cumulative exposure to indoor air dampness microbiota in moisture-damaged buildings and daily exposure to wireless telecommunication devices would potentiate the risk of electromagnetic hypersensitivity (EHS), which is poorly defined. We performed a nested comparative analysis within an age- and sex-matched study of females who were exposed to dampness microbiota with self-reported complaints compatible with EHS (n=11). Their levels of autoantibodies towards 13 different autoantigens were measured. EHS presented as multiple chemical sensitivity, profound fatigue, memory disturbances in all subjects (11/11), and cognitive impairment in the majority (9/11). When comparing the patients to controls, no difference was detected between the levels of the following autoantibodies: angiotensin II type 1 receptor (AGTR1), endothelin receptor type A (ETAR), adrenergic receptors α1AR, α2AR, β1AR, β2AR and cholinergic muscarinic receptors m1AChR, m2AChR, m3AChR and m5AChR. In contrast, IgG levels towards m4AChR and fibroblast growth factor receptor 3 (FGFR3), and IgM autoantibodies against glycosylated moieties of heparan and heparan sulphate (TS-HDS) were significantly decreased in the study cohort, p=0.008; p=0.032, p<0.001, respectively. This is the first report demonstrating an imbalance in the nervous system autoantibodies in patients with EHS. The clinical significance of these altered responses remains to be clarified.