Alzheimer’s Disease (AD) is a multifactorial process. Amyloid plaque formation constitutes the main characteristic of the disease. Despite the identification of numerous factors associated with AD, the mechanism remains unclear in several aspects. Disturbances in intestinal and blood–brain barrier (BBB) penetration, observed in AD, may facilitate immunologic response to food-derived antigens. In the present study, antibodies against egg albumin, bovine-casein, and N-Glycolyl-Neuraminic acid (Neu5Gc) were measured in the cerebrospinal fluid (CSF) and serum of the patients using an enzyme-linked immunosorbent assay (ELISA). Zero anti-Neu5Gc and low concentrations of anti-casein antibodies were detected. Increased anti-native egg albumin antibodies were present in the serum of patients of all stages with 65% positivity (p < 0.001) in mild disease and a higher percentage in females (81.9%, p < 0.001). Lower serum positivity to anti-denatured egg albumin antibodies was observed, showing a gradual increase with severity and higher prevalence also in females. In the CSF, anti-native and anti-denatured egg albumin antibodies were mainly observed in severely ill patients with accumulative positivity to either antigen, reaching 61.8% in severe vs. 15% in mild disease (p < 0.001). Increased values were mainly observed in males. Anti-egg albumin antibodies may be implicated in the disease mechanism through sequence/structural similarity with human proteins, mainly serpins, and it would be worth consideration in further investigations and therapeutic strategies.