Allergic Colitis | Symptoms & Causes

While symptoms may not appear until a baby turns 6 months old, most babies show signs within the first two months of life. In most babies, the symptoms start off mild and gradually worsen.


A baby with allergic colitis seems extremely fussy, difficult to console and has bloody stools. Some infants also have diarrhea and vomiting, and some may show other signs of allergies, such as nasal congestion or eczema. It’s important to remember that allergic colitis falls on a spectrum — some babies are much more sensitive to milk protein (and have much more severe symptoms) than others.


Many babies go through a period of reflux (spitting up food), between ages 4 and 6 months, but babies with allergic colitis may have an especially hard time with reflux. This means that even when following a dietitian’s recommendations, your baby may still become irritable. This doesn’t mean the allergic reactions are back.

Medication can help a baby’s reflux until they outgrow it. This usually happens by the time they can sit up by themselves, around 7 months old.


What are the causes of allergic colitis?

Allergic colitis seems to be caused by a combination of changes to the mother’s immune system during pregnancy, and the immaturity of a baby’s own immune system. But it’s not yet known why some babies develop the condition and others don’t.

There may be a hereditary component, since babies who come from families with a history of food allergies, asthma or environmental allergies seem to be more likely to have allergic colitis.