Hello 4 Month Old Has Had Eczema On Cheeks And

Hello 4 month old has had eczema on cheeks and has a small patch on chest. The dry skin on cheeks is the worse. Sometime it oozes clear liquid from him scratching. He also has a red ring around his anus. I was thinking milk allergy but he doesnt seem uncomfortable. He pretty much content all the time. I do notice him having a hard time having a bowel movement. He grunts a lot. Could it be a milk allergy?