A milk allergy is an immune reaction to one of the many proteins in animal milk, although it is most often caused by the alpha S1-casein protein in cow's milk.

A milk allergy is sometimes confused with lactose intolerance because they often share symptoms. The two conditions are very different, however. Lactose intolerance occurs when a person lacks the enzyme (lactase) to metabolize lactose—a milk sugar—in the intestines.

Cow's milk is the leading cause of allergic reactions in young children and one of eight foods that are responsible for 90 percent of childhood allergies. (The other seven are eggs, peanuts, tree nuts, soy, fish, shellfish, and wheat.)

Symptoms

Often, children with a milk allergy will have a "slow" reaction, which means symptoms will develop over time—perhaps within several hours to days later. Symptoms associated with a slow reaction are:

  • abdominal cramps
  • loose stool (which may contain blood or mucus)
  • diarrhea
  • skin rash
  • intermittent coughing
  • runny nose or sinus infection
  • failure to thrive (slow to gain weight or height)

Symptoms that occur quickly (within seconds to hours) may include:

  • wheezing
  • vomiting
  • hives

Although rare, it is possible for a child with a milk allergy to have a serious reaction known as anaphylactic shock. Anaphylactic shock may cause swelling of the throat and mouth, cause a drop in blood pressure, impede breathing, and can lead to cardiac arrest. Anaphylaxis requires immediate medical attention and is treated with epinephrine (EpiPen) in the form of a shot.

Rice Milk Allergies

Rice is the least likely grain to cause an allergic reaction (hypoallergenic), therefore many parents choose to give their children rice milk instead of cow's milk due to allergy concerns. While rice allergies are extremely rare in the West, they have been on the rise in Asian countries such as Japan and Korea, where rice is a staple food, since the 1990s.

Symptoms of rice allergy include:

  • redness of the skin
  • rashes
  • hives
  • swelling
  • stuffy or runny nose
  • wheezing
  • anaphylaxis

Almond Milk Allergies

Switching from regular milk to almond milk may be trading one allergic reaction for another. Tree nuts such as almonds (along with walnuts, cashews, and pecans) top the list of allergy offenders. In addition, nearly half of people allergic to peanuts are allergic to tree nuts.

Unlike a cow's milk allergy, which typically resolves at a very early age, tree nut allergies tend to last a lifetime. Only 9 percent of children will outgrow an allergy to almonds and other tree nuts.

Symptoms of a tree nut allergy may include skin reactions including:

  • itching
  • eczema or hives
  • swelling
  • nausea
  • abdominal pain
  • diarrhea
  • vomiting
  • runny nose
  • wheezing
  • trouble breathing

It is also more common to suffer an anaphylactic reaction to tree nuts (and peanuts) than with other types of allergies.

Breast Milk Allergies

Breastfeeding provides the best source of nutrients for a baby and helps her to develop to develop defenses against certain allergies.

A mother who drinks cow's milk, however, will transfer the alpha S1-casein  and whey protein to her child via her breast milk, possibly causing a reaction in an allergic baby. Milk allergies are usually discovered very early in breastfed infants.

The good news, however, is that babies who are breastfed have fewer allergies and infections during the first year than do those who are given formula.

Most doctors recommend new mothers nurse for at least the first six months of a child's life to help the infant avoid allergies.

Soy Milk Allergies

Again, soy is one of the "big eight" allergens, so it is important to watch for symptoms, especially in children. Soybeans, along with peanuts, kidney beans, lentils and peas, are in the legume family.

A soy allergy is most common in infants.

Symptoms of a soy allergy may include:

  • flushing
  • itching
  • hives
  • runny nose
  • wheezing

In more serious reactions, abdominal pain, diarrhea, and swelling of the lips, tongue, or throat may occur. In vary rare cases, a soy allergy may result in anaphylaxis.

In Children, Infants, and Toddlers

Allergies are usually discovered very early, often by three months of age. As noted, breastfeeding is one of the best ways to avoid and defend against allergies. A newborn should not be given any formula during the first four weeks after birth, but when breastfeeding isn't an option, certain formulas can usually be safely tolerated by infants.

Formula for Babies With Milk Allergies

Most pediatricians recommend soy-based formulas with added vitamins and minerals for babies allergic to milk.

If symptoms don't improve after a switch to soy, "hypoallergenic" formulas are available, including extensively hydrolyzed formulas in which proteins have been broken down so they are less likely to cause a reaction.

The other type of hypoallergenic formula commonly used is known as an elemental formula, in which only the simplest forms of protein are used.