Thirty male Sprague-Dawley (SD) rats, weighing 230 ± 20 grams and aged 2 to 3 months (equivalent to human juveniles to young adults), were procured from the Laboratory Animal Center of Sun Yat-sen University. The animals were housed under strict dietary standards, with feed provided and drinking water consisting of pure water from the Laboratory Animal Center. Prior to the intervention, all animals underwent a 7-day acclimatization period and were fed accordingly. Hairy areas, such as the neck, were shaved in preparation for the study. The standard feed consisted of Ovalbumin Punch, sourced from Xiangtan Jiayeyuan Biotechnology Co., Ltd., which is food-grade, egg-yellow powder with 98% active substance content, adhering to Good Manufacturing Practice (GMP) standards (E. coli and Salmonella negative), and within the validity period. Lactose was purchased from Hebei Baiyi Biotechnology Co., Ltd., also food-grade with 99% active substance content, GMP compliant (E. coli and Salmonella negative), and within the validity period.

Rats were randomly assigned to three groups: experimental, lactose, and control, with 10 rats per group. The experimental group received 1 mg/mL ovalbumin via gavage (1 mL/day), the lactose group received 2 mg/mL lactose via gavage (1 mL/day), and the control group received saline via gavage (1 mL/day). Throughout the modeling period, rats had ad libitum access to food and water, and gavages were administered daily at 8:30 a.m. to monitor trait variations. In the experimental group, ovalbumin was administered orally without adjuvant to induce the food allergy model. After 50 days of continuous gavage, a single dose of 100 mg ovalbumin was given on the 51^st day to stimulate the model, and a single dose of 100 mg lactose was given to the lactose group. One hour post-gavage, 1 mL of blood was collected from the ocular venous plexus, and serum was separated and stored at −20˚C for subsequent analysis.

Allergic symptoms were observed and scored continuously for 60 minutes in both groups. Skin reaction scoring criteria were as follows: grade 0, no symptoms; grade 1, nose and head-scratching; grade 2, periocular and perioral edema; grade 3, trunk and limb edema; grade 4, skin petechiae and hair standing. Intestinal reaction scoring criteria were: grade 0, no symptoms; grade 1, reduced appetite; grade 2, diarrhea. Each grade corresponds to a specific score.

Serum IgG4 and IgE antibody levels were determined using the ocular venous plexus blood collection method and Enzyme-Linked Immunoassay (ELISA), following the manufacturer’s instructions precisely.

Glomerular basement membrane changes were observed microscopically. Thickening of the glomerular basement membrane and glomerular ischemia were considered positive lesions; normal conditions were negative. Kidney tissue served as antigen, and Anti-Glomerular Basement Membrane (AGBM) antibody was measured by indirect immunofluorescence, with normal conditions being negative.

After 61 days of stimulation, among the 10 rats in the ovalbumin group, 3 exhibited poor appetite and 1 displayed diarrhea. In the lactose group, 2 out of 10 rats showed poor appetite, while all 10 rats in the control group presented mild symptoms. The difference in intestinal manifestations between the ovalbumin group and the control group was statistically significant (P < 0.01). Additionally, there was a significant difference in serum IgE levels between the ovalbumin and lactose groups (P < 0.01). A significant difference was also observed when comparing the lactose group with the control group (P < 0.05). For detailed data, refer to Table 1 .

Note: Compared with control group, *P < 0.05, **P < 0.01; compared with lactose group, ^ΔP < 0.05, ^ΔΔP < 0.01.

In the ovalbumin group, 3 out of 10 rats scored 3 on the scale for paleness around the mouth and tail; 5 scored 2 for swelling around the eyes or mouth, and 2 scored 1 for nose scratching and head scratching. In the lactose group, 1 rat scored 2 for swelling around the eyes or mouth, and 2 scored 1 for nose and head-scratching. The control group of 10 rats had mild symptoms. The differences in skin reactions between the ovalbumin group and the control group were statistically significant (P < 0.01). There was also a significant difference in serum IgE levels between the ovalbumin and lactose groups (P < 0.01), and between the lactose group and the control group (P < 0.05). See Table 1 for specific values.

The serum IgE level difference between the ovalbumin group and the control group was highly significant (P < 0.001), and the same comparison with the lactose group also yielded a significant difference (P < 0.01). Serum IgG4 levels showed a significant difference between the ovalbumin and lactose groups (P < 0.05), but no significant difference was observed when compared with the control group (P > 0.05), as detailed in Table 2 . The lactose group did not show a significant difference in serum IgE compared with the control group (P > 0.05), yet a significant difference in serum IgG4 was noted (P < 0.05), as shown in Table 2 .

Note: Compared with control group, *P < 0.05, **P < 0.01; compared with lactose group, ^ΔP < 0.05, ^ΔΔP < 0.01.

The positive rate of anti-glomerular basement membrane antibody expression in the glomerular basement membrane sections of rats in the ovalbumin group was significantly higher than that in both the control and lactose groups (P < 0.01) (see Table 3 ). This finding may be associated with the formation of large molecule immune complexes in vivo, potentially leading to the deposition in the kidneys, thickening of the glomerular basement membrane, and the development of various forms of nephritis, ultimately causing further renal damage.