My friends baby is always sick

One of my friends has a baby girls I think she is like 4 months old but she is always sick. This is the third time she got sick. 🥺 for me this is not normal and I really want to help. This time she is sick and puking 🤢 a lot it’s been a week: I don’t know what the cause is but I though maybe you guys know or have an idea and can share.