Girls, could you please tell me if this is an allergic reaction in a c…

Girls, could you please tell me if this is an allergic reaction in a child? The baby is 2.5 weeks old. I haven't introduced anything new to his diet, I eat as before. Redness appeared on his belly in the morning, now it has appeared on his legs and face. But the baby is not bothered. Thanks in advance for your answer!