You can find a lot of different textures, colors, and odors in a baby’s poopy diaper based on what he’s eating (breast milk, formula, or solid foods). The poop is normally much softer than an adult's, and it’s not uncommon for it to be even softer than usual sometimes. But if it suddenly gets much looser or more watery, and happens more often and in large amounts, it may be diarrhea.

Baby Diarrhea Causes

A lot of things can cause the problem, including:

An infection with a virus, bacteria, or parasite. Babies can pick up these germs through contact with unclean food or water or when they touch germy surfaces and then put their hands into their mouths.
A food allergy or sensitivity to medicines
Drinking too much fruit juice
Poisoning
Baby Diarrhea Treatments

Doctors usually don't recommend over-the-counter anti-diarrheal medicines for children. However,But your doc might prescribe an antibiotic for a bacterial infection or an anti-parasitic drug for a parasite infection.
Babies with severe diarrhea who get dehydrated will need to go to a hospital to get fluids through an IV in their veins.
The doctor might recommend that you give your baby an oral rehydration solution. These products, which you can buy at the supermarket or drug store, have fluids and electrolytes and can prevent or treat dehydration.
If your child eats solid foods, the doctor might recommend switching to bland, starchy foods like strained bananas, applesauce, and rice cereal until the diarrhea stops. Mothers who are breastfeeding might need to adjust their own diet to avoid any foods that could trigger diarrhea in their babies.
Babies with diarrhea should avoid eating anything that can make it worse, including:

• Greasy foods
• Foods that are high in fiber
• Dairy products such as milk and cheese
• Sweets such as cake, cookies, and soda

Source​ ៖ www.webmd.com