Allergic Proctocolitis

What is Allergic Proctocolitis?

If my story sounds familiar, your baby may have Allergic Proctocolitis (also called Milk/Soy Protein Intolerance, Dietary Protein-Induced Proctocolitis, and many other complicated names!) Proctocolitis is inflammation of the lower part of the intestines. If the inflammation is caused by an allergic reaction, it is called Allergic Proctocolitis. Note: while this condition is often referred to as a food sensitivity, hypersensitivity reaction, or intolerance, it is, technically, an allergy.

Symptoms of Allergic Proctocolitis

The main symptom of Allergic Proctocolitis (AP) is mucus with visible specks or streaks of blood in dirty diapers (stools). The stools may be watery, and they are often green. Many infants with AP are very fussy. It is not uncommon for families to be told their baby has colic. Bouts of crying (day and night), poor sleep, and obvious discomfort after eating can be a part of AP too. Some babies with AP have skin rashes or eczema, although these are more common with other kinds of allergic reactions.

If you don’t see any blood, but there is mucus and misery, your doctor can test a sample of stool to see if there is invisible (occult) blood. AP usually shows up in the first 2 months of life.

Babies with Allergic Proctocolitis DO NOT throw up regularly, and they don’t have a lot of diarrhea. They grow and develop normally and don’t show signs of malnutrition. More serious symptoms could be caused by a different kind of food allergy, or another medical issue. It is important that you let a health care provider know what is going on.

Causes of Allergic Proctocolitis

Our intestines do more than just digest food and absorb nutrients. They are also the first line of defense against germs and other things we swallow that could be bad for our bodies. Healthy, mature guts can tell the difference between “friends” and “enemies”. If our body makes a mistake and attacks a “friend”, we have an allergic reaction. Perhaps because their intestines have not finished maturing, or for some other reason we don’t yet understand, some infants have allergic reactions to parts of foods called proteins. If you are breastfeeding, proteins from the foods you eat enter your breast milk. Your baby can have a reaction to these proteins, causing swelling and irritation of the lower intestines. At least half of all cases of AP are caused by a reaction to cow’s milk (dairy) proteins. Soy protein is the second most common cause, and many babies have a problem with both dairy and soy. Other less common allergens are corn and egg. Note: Any food protein can cause an allergic reaction. Work with a Registered Dietitian or other experienced health care provider to find the food or foods to which your baby reacts.

At this time, no one knows why some babies get AP. The condition does not seem to be related to prematurity, the health of the mother, or her diet while pregnant. It may be more common in male babies than female. Only about one quarter of babies with this condition come from families with known food allergies.

How Common is Allergic Proctocolitis?

While no one knows exactly how many babies have Allergic Proctocolitis(AP), we do know that 2 or 3 children out of every 100 will have some kind of allergic reaction to milk (in exclusively breastfed infants, this number falls to 1 in 100 (1%) or less). Around 1 in 100 children will be allergic to soy, but not all of these allergies are AP. Unlike other allergic reactions, AP is more common in exclusively breastfed infants than those being fed formula.


If you are concerned about your baby’s health, see a doctor as soon as possible. It is important to rule out other, possibly more serious, conditions. The doctor should take a detailed health history and give your baby a full physical, including measurements to make sure your baby is growing well. [Note: it is not how large or small a baby is for its age that matters! If the height, weight, and head circumference follow one of the curves on the growth chart, the baby is growing normally.] Testing stool samples is common, and some doctors may ask for a blood test. Your doctor may refer you to a specialist such as a pediatric gastroenterologist or a pediatric allergist. Some doctors recommend a test called an endoscopy (en-DOS-copy) to look inside the baby’s intestines, and may take a tiny sample of intestinal tissue for testing (a biopsy).

Here are some tests your health care practitioner may run, and what they are looking for:

Common Tests

Less Common Tests

Stool sample

   Looking for:

  • infections (viruses, bacteria) that could cause bleeding and diarrhea
  • blood you cannot see (occult blood)
  • signs of allergy



  • to confirm diagnosis
  • to rule out other problems



  • to test intestinal tissue
  • to confirm signs of an allergic reaction

Blood test

   Looking for:

  • anemia (low blood iron levels)
  • low levels of vitamins or minerals (indicating that food is not being properly absorbed)
  • low levels of protein in the blood (hypoalbuminemia)
  • signs of allergy in the blood (usually negative with AP)



  • to rule out other problems

Skin Prick Tests/RAST


  • to look for signs of allergy outside of the intestines (usually negative with AP)

Your baby definitely has AP if removing the problem protein from his diet makes his symptoms go away. Your doctor will use this process, called an elimination diet, to both diagnose and treat AP.

Author’s Note: While Allergic Proctocolitis is becoming better understood and better known, there is still a lack of knowledge in some segments of the health care community. If you do not feel that your doctor is giving your baby the attention deserved, be persistent. This website was designed to educate healthcare professionals as well as families. If your doctor would like more information, feel free to refer him or her to the “Health Practitioner” section of this site. If all else fails, ask for a referral to a specialist, or find another physician who will take your concerns more seriously.


The treatment for Allergic Proctocolitis (AP) is to avoid the food(s) that cause the problem. If you are breastfeeding and a health care practitioner thinks your baby has AP, you will need to stop eating foods that bother your baby. Note: If your baby takes formula, please see the FAQ section.

Since more than half of all AP cases are caused by cow’s milk, dairy is the best place to start. Babies who are sensitive to dairy are often sensitive to soy as well, so many doctors recommend removing both dairy and soy from your diet right away. This web site offers detailed instructions for dairy and soy elimination diets (see the Handouts section for printable information on these diets). Making these changes can be difficult. A Registered Dietitian can help you learn what foods to avoid, how to put safe meals together for you and your family, and how to make sure you stay healthy in the process.

How long will it take for my baby to feel better?

Studies show that many babies will stop bleeding as soon as 2 or 3 days after you stop eating the offending protein(s). Experience has shown, however, that the longer the baby has been bleeding, the longer it takes for their intestines to heal. While some practitioners recommend trying the elimination diet for only 1 to 2 weeks, it can really take 1 to 2 months for all symptoms to go away. If you are not seeing ANY improvement after 2 weeks on an elimination diet, see the FAQ section.