A lot of confusion exists between the two adverse reactions - milk allergy and lactose intolerance, both attributable to milk.
What are lactose intolerance and milk allergy?
Lactose or milk intolerance is non-allergic food sensitivity and occurs due to the decrease or absence of lactase enzyme that is required to metabolise the milk sugar lactose. It the commonest type of carbohydrate intolerance found among adults of African, Asian, Native American or Chinese descent.
It develops in children around the age of five years due to the partial or complete loss of this enzyme due to some unknown reasons. Children below the age of five who suffer from a severe attack of diarrhoea or another severe illness could also develop temporary or permanent lactose intolerance.
Milk allergy is an adverse reaction triggered by immunoglobulin E (IgE) antibodies to one or more of the proteins in cow's milk. People can be allergic to either whey or casein protein, or both, and an allergic reaction can be elicited by very small amounts of these allergen proteins in sensitive people. Heat treatment, such as pasteurisation, breaks whey protein, so people allergic to whey might not react to pasteurised milk.
But casein is heat stable, so people allergic to casein will probably react to all types of milk and milk products. Most people are allergic to both the casein and whey fractions indicating that most milk-allergic people cannot tolerate boiled milk. Allergy to milk may occur in any individual. Young children are most commonly affected although one can develop milk allergy at any age.
How common are lactose intolerance and milk allergy?
About 5% of the general population in the UK suffer from lactose intolerance. A much bigger proportion of people are affected in the communities that do not include milk in their traditional adult diet. For example, up to 75% of the black African community and more than 90% of the Asian community are intolerant to lactose. Between 30 and 50 million Americans are lactose intolerant, and some ethnic populations are more affected as compared to others.
Up to 80 percent of African Americans, 80 to 100 percent of American Indians, and 90 to 100 percent of Asian Americans are lactose intolerant. The condition is found to be least common among people of northern European descent. It is usually commoner in older people, since body produces fewer lactase enzymes with advancing age.
Researchers claim that allergy to milk develops between 1% and 7% of children. Up to 60% of infants allergic to milk surpass this allergy by the age of 4 and 80% by the age of 6. Milk allergy is seen to be much less frequent in adults with incidence of just 0.1-0.5% in adulthood.
Symptoms of lactose intolerance and milk allergy
The common symptoms of lactose intolerance range from mild to severe and include nausea, vomiting, bloating, abdominal cramps, gas, diarrhea, weight loss and malnutrition. Symptoms begin about 30 minutes to 2 hours after consuming a lactose containing product. The severity of symptoms depends on the amount of lactose containing product consumed, the degree of deficiency of lactase enzyme in the body, and a person’s age, ethnicity and digestion rate.
The symptoms of milk allergy may occur within a few minutes after exposure in immediate reactions, or after hours to several days in delayed reactions. This allergy is capable of triggering a wide array of symptoms which include GI reactions - nausea, vomiting, diarrhea, abdominal cramps, gas, and heartburn; nose, ear and throat infections – runny nose, sinusitis, and coughing; and symptoms involving the skin - itchy rash, hives and eczema. In a very few cases, milk allergy can cause anaphylaxis.
Diagnosis of lactose intolerance and milk allergy
It can be hard to diagnose lactose intolerance based on symptoms alone. The doctor may first recommend eliminating cow’s milk from the diet to see if the symptoms go away. There are no blood tests to back the diagnosis of lactose intolerance. In infants and young children, a stool sample can be tested for the presence of acids and glucose in the stool. Undigested lactose fermented by gastrointestinal bacteria produces lactic acid and other fatty acids that get detected in a stool sample. Carbohydrates may be present in the stool indicating malabsorption of lactose.
Other diagnostic tests are the lactose tolerance test and the hydrogen breath test; they are not suitable for infants that can't drink too much lactose. In the hydrogen breath test, the patient ingests a quantity of lactose and a breath sample is analysed for the presence of hydrogen. Lactose intolerance test is a confirmatory test for lactose intolerance.
The diagnosis of milk allergy in infants is quite straightforward in case the symptoms developed immediately after the child was put on milk formula made from modified cow's milk or soon after a person consumed milk-containing food. Milk allergy gets tough to diagnose in older children and adults because milk is usually consumed along with other food.
Diagnosis of food allergy requires a combination of complete clinical history, laboratory (such as specific IgE measurements) or outpatient (skin prick tests) tests and challenges with the food. Only the milk reactions that develop soon after the consumption of milk products are very likely to give a positive blood or skin test, as they detect IgE that is responsible for the immediate-type reaction. They yield negative results in patients with non-IgE mediated responses.
Treatment of lactose intolerance and milk allergy
The level of dietary control in lactose intolerance depends on the amount of lactose a person’s body can tolerate. In infants and young children, calcium supplementation may be required, as milk may be their only source of calcium. The American Dietetic Association recommends calcium requirements are 400 mg/day for 0–6 month’s infants and 600 mg/day for a 6–12 months old child. Lactose-reduced milk and other products are available in the market. A tablet is also available without prescription that can be taken with a lactose-containing food to supply lactase for breaking down lactose. This tablet should be taken with the first bite of a dairy product.
Avoidance of milk and milk-containing foods is the only treatment. It can be really tough as milk is a common food ingredient. Medications, such as antihistamines, may calm down signs and symptoms of a milk allergy. These drugs control an allergic reaction after exposure to milk and help relieve discomfort. Other drugs, such as sodium cromoglycate and corticosteroid drugs prevent the development of symptoms of eczema to develop. In case of a serious allergic reaction such as anaphylaxis, a child may need an emergency injection of epinephrine and quick admission to the emergency room. You may also be required to carry injectable epinephrine at all times.
Prognosis of lactose intolerance and milk allergy
The outlook for people with lactose intolerance is considered to be excellent. The symptoms usually go away with the removal of milk products from the diet or by consuming milk products along with a dose of commercially-prepared lactase enzyme.
Majority of children outgrow milk allergy after avoiding milk for 12-18 months. Thus the prognosis is good, with remission rates of about 45-50% at 1 year of age, 60-75% at 2 years and 85-90% at 3 years. Thus 9 out of 10 sufferers outgrow this allergy by the age of 3. But individuals who develop the allergy later in life will probably retain it.