My 6month old baby is suffering from loose motion since last 15 days?

Virus or allergies: I am thinking loose stools is what you mean, and no fever or vomiting? Has he started solids, or changed his diet recently? Loose stools are often a sign of food sensitivity. If you have just switched him to dairy formula or are trying out new foods, try to eliminate them one at a time to see if he returns to normal. If not, follow up with your doc.