FeaturesApr/May 2012 Issue

Milk Allergy

We answer your top questions about dairy allergy and lactose intolerance

© Thinkstock 2012/iStockphoto

© Thinkstock 2012/iStockphoto

 

If you have a dairy allergy, chances are you’ve heard this question many times: So, you’re lactose intolerant, right?

Those with dairy issues commonly encounter confusion over milk intolerance and milk allergy. Over the years, I’ve received questions from relatives who can’t understand why tiny amounts of milk could be deadly for me, from new acquaintances who are curious about my dietary needs and from restaurant waitstaff who are confused by my special-diet requests. Sound familiar?

To get to the bottom of this widespread confusion, we compiled your top questions (and mine) and put them to some of the nation’s leading allergists who specialize in milk allergy. We hope that this information helps you understand dairy issues better and gives you the tools to educate those around you.

What’s the difference between lactose intolerance and dairy allergy?

“A milk allergy involves an attack on milk protein by the immune system, the part of the body that fights infections,” explains pediatric allergist Scott Sicherer, MD, author of The Complete Idiot’s Guide to Dairy-Free Eating. In most cases, a type of antibody known as IgE (immunoglobulin E) responds to milk protein as if it’s a dangerous invader, triggering a cascade of immune response that causes potentially dangerous symptoms.

In contrast, says Sicherer, “a milk intolerance, also called lactose intolerance, is trouble with digesting the sugar in milk.” Lactose is the milk sugar and lactase is the enzyme that digests it. Unlike an allergy, dairy intolerance involves problems in the digestive system that stem from this missing enzyme.

How common are milk allergy and lactose intolerance?

Data on milk allergy prevalence is relatively limited. Evidence suggests that in Westernized countries, about 1 to 2 percent of children have experienced a milk allergy, which most ultimately outgrow. Milk allergy is found more commonly in boys than girls. “For lactose intolerance, persons of Asian descent have the highest rate—over 90 percent,” says Sicherer. “Additionally, about 70 percent of Native Americans and African Americans have lactase deficiency. Thus, being lactose intolerant is basically the norm for adults worldwide. However, rates are lowest (5 to 20 percent) among Caucasian adults.”

When do these problems generally develop?

“Milk allergy most often has an early onset,” explains Robert Wood, MD, chief of pediatric allergy and immunology at Johns Hopkins Hospital in Baltimore. “It most often develops by one year of age. The majority of milk allergy will be outgrown by age 5 or 6; only about 10 to 20 percent will keep it for their entire lifetime.”

In the case of lactose intolerance, babies and young children usually have sufficient amounts of the lactase enzyme to digest milk sugars. However, the amount of lactase produced by the body decreases over time. Thus, dairy intolerance more commonly develops in later childhood and adulthood and once established, it’s less likely to resolve.

© Radius Images/Alamy

© Radius Images/Alamy

How do symptoms differ between an allergy and an intolerance?

An allergic reaction to milk generally involves multiple body systems, affecting the skin, lungs, digestive system and circulatory system. Symptoms can include:

  •  itchy rashes,
  • hives,
  • swelling (often of lips and face),
  • wheezing,
  • throat tightness,
  • trouble breathing,
  • trouble swallowing,
  • abdominal pain,
  •  vomiting,
  • diarrhea,
  • paleness/weakness,
  • confusion,
  • fainting,
  • low-blood pressure.

Allergic symptoms usually begin minutes to an hour after ingestion. A very small amount of milk can potentially trigger a reaction. Thus, those with a milk allergy typically need to avoid milk completely.

In contrast, lactose intolerance generally involves only gastrointestinal symptoms, including:

  • abdominal bloating,
  • abdominal cramping,
  • gas,
  • vomiting,
  • diarrhea.

These symptoms can occur up to several hours after ingesting dairy. Those with lactose intolerance may be able to eat small amounts of milk without a problem.

How can you tell whether you’re experiencing an allergy or intolerance?

One of the main causes for confusion stems from the fact that both milk allergy and dairy intolerance can cause gastrointestinal symptoms.

“There are two main ways to differentiate in people who are having abdominal pain,” explains Wood. “First, it’s rare for someone with an allergy to have just abdominal pain. Usually, there are other symptoms, such as hives or other rashes, breathing difficulty or anaphylaxis. Second, it’s likely that an allergy would cause problems with much smaller doses of dairy than an intolerance.”

Another important indicator, says Jennifer Kim, MD, a pediatric allergist at Mount Sinai Medical School, is the timing of symptoms. “A dairy allergy is generally a more immediate reaction,” she says. “Symptoms occur right away or at least within an hour or two of ingestion. In lactose intolerance, they can develop over several hours after ingestion.”

How is each condition diagnosed?

Usually, a physician can determine whether someone is experiencing an allergy or an intolerance based solely on their symptoms and other factors, such as their age and ethnic background. If it’s unclear or more information is needed, there are diagnostic tests available.

In the case of suspected lactose intolerance, a doctor can administer a lactose tolerance test or a hydrogen breath test. Either test can detect whether someone is properly digesting lactose. Alternatively, a doctor may simply recommend cutting dairy out of the diet to see if symptoms improve.

Diagnostic testing for a dairy allergy would include blood tests to measure the amount of IgE antibodies in the blood that respond to milk proteins. In addition, an allergist may order skin prick testing, in which a small drop of milk extract is placed on the skin to see if it causes a local reaction. The most conclusive test is a food challenge, in which a person eats small amounts of milk to determine whether it causes symptoms. Food challenges should always occur under the supervision of a board-certified allergist with emergency medications on hand in case of a severe reaction.

How and why do milk allergies vary between individuals?

Milk allergies differ from person to person both by the severity of the reaction and the specific symptoms that result.

“In every person who has a milk allergy, IgE antibodies bind to different parts of the protein, depending on the individual,” says Kim. These subtle differences at the molecular level are the reason allergic individuals can experience very different reactions from one another and why some can tolerate milk in baked goods and others can’t.

In addition, people may be allergic to either or both major milk proteins: casein and whey. Casein makes up about 80 percent of milk protein; whey accounts for the remaining 20 percent.

Although casein is thought to be more allergenic than whey, the specific protein causing the allergy is not relevant to the care and treatment a milk-allergic person receives. Thus, allergists don’t test for it.

What about other animal milks, like goat’s milk or sheep's milk? Why can some dairy-allergic people drink goat’s milk while others can’t?

“Most people—over 90 percent—who are allergic to cow’s milk will also react to most of the other mammalian milks,” says Sicherer. “We think this is simply because the proteins are similar.” Those with severe dairy allergy should not try other animal milks except under close medical supervision.

What treatment and dietary changes are necessary?

For lactose intolerance, treatment is relatively straightforward and involves avoiding milk products, taking supplemental lactase enzyme (via a pill) or using lactose-free products (such as Lactaid® milk). Some dairy products, such as cheese, yogurt and ice cream, may be easier to digest because they naturally contain less lactose.

Dairy allergy is much more serious and requires guidance and monitoring by a board-certified allergist. An allergist helps a patient develop a detailed care plan based on the specific severity and symptoms of their milk allergy. Avoidance of any exposure to milk products is the most important management strategy.

You may need to carry doses of antihistamines to control symptoms in the event of accidental exposure. Depending on the severity, your allergist may also prescribe an epinephrine auto-injector, which can be used to temporarily treat symptoms in the event of a severe reaction, giving you time to get to a hospital.

Unlike a dairy intolerance, there are no supplements or special types of milk products you can use to prevent an allergic reaction to dairy. However, there are various milk substitutes available, made with plant “milks” such as rice, coconut, soy, hemp and nuts. This includes substitute yogurts, ice creams and cheeses.

Due to the lack of dairy products in the diet, it’s important in both cases to get calcium from other sources, such as other calcium-rich foods (leafy greens, broccoli, some types of fish or shellfish, etc.), calcium-enriched juices and calcium supplements.

What’s the latest research on anaphylactic dairy allergy? Is there some promising treatment on the horizon?

Important research is being conducted around the country with promising preliminary results based on small sample sizes. Essentially, these studies are investigating oral immunotheraphy, a treatment for milk allergy where study participants are given small amounts of milk in gradually increasing doses over time to try to alter the immune system’s response to the allergen.

“We’re doing a study of milk oral immunotherapy and we’re testing whether adding omalizumab (an anti-IgE treatment used for asthma) helps patients, as well,” says Sicherer, describing ongoing research at the Mount Sinai Medical Center.

What’s known so far? “What is clear is that oral immunotherapy is not tolerated by everyone. There are side effects and it is still an open question whether it can make a milk allergy permanently end or whether it simply allows for an increased threshold before a reaction does occur,” says Sicherer.

It is important to note that this type of therapy is under investigation. Although initial results are promising, it is not an FDA-approved treatment and it should not be tried at home under any circumstances.

Joshua Feblowitz, who has severe milk and nut allergies, is a freelance medical writer and a student at Harvard University Medical School.

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