5- Infant colic
Abnormal gut bacteria in infants may be one cause of colic, or excessive crying, recent research suggests.
In the study, colicky babies (who cry for more than three hours a day without a medical reason) had a distinct bacterial "signature": They had higher numbers of bacteria from a group called Proteobacteria in their guts compared to babies without colic.
Proteobacteria include bacteria known to produce gas, which may cause pain in infants and lead to crying, the researchers said.
These abnormities disappeared after the first few months of life, which suggests they are temporary. However, this study was small and conducted for just a few months, so additional, longer studies are needed to confirm the results.https://www.livescience.com/39444-gut-bacteria-health.html