Can a newborn take a single pill of medication at once? Is there any problem with this?

The baby is seven and a half months old and has had diarrhea for three months. The stools are loose, occurring 3 to 5 times a day, sometimes with mucus but no blood. The baby looks normal and is in good spirits. Could this be an intestinal inflammation? Is it a physiological lactose intolerance? How should it be treated?

The child was weaned at eight months old and started adding formula milk and complementary foods at around seven months. He had no diarrhea after eating apple puree, rice porridge, and quail egg yolks. However, after adding a serving of pea puree, the child experienced symptoms of indigestion and anorexia. According to the situation, this may be related to gut microbiota imbalance. It is recommended to try taking Lactase or other probiotic medications to regulate gastrointestinal function.