Your son is likely suffering from chronic constipation, which is common in young children, but can become severe when stools are passed only once every 6 to 7 days with pain. Looz oral solution, which contains lactulose, is an osmotic laxative. It works by drawing water into the bowel, making stools softer and easier to pass. In children, it is generally considered safe and is often prescribed for long-term use under medical supervision. However, medicines alone are not enough. A poor appetite and lack of weight gain for 1.5 years need proper evaluation. This may be linked to ongoing constipation, low fibre intake, inadequate calories, or occasionally underlying medical conditions. Along with lactulose, your child should have more fluids, more fruits and vegetables, and regular meal times. It is important to follow up with a paediatrician to monitor growth and response to treatment. With the right combination of dietary changes, routine, and medication, most children gradually improve.