Dairy Allergy vs Lactose Intolerance

Lactose is a sugar found only in milk. When we eat or drink lactose, it‘s broken down by an enzyme called lactase in the small intestine. Lactase is very important for babies who are entirely reliant on being able to digest their mother’s milk to get the energy they need to grow. Once we eat a full diet Lactase becomes less necessary, and lactase levels tend to fall naturally as we get older. Lactose intolerance symptoms are very rare in children under 6 (amongst whom cow’s milk protein allergy is more common) but get more and more common as we grow older. Lactose intolerance, which is different to lactose allergy, occurs when there is not enough of the enzyme to digest the milk properly.

If the lactose isn’t broken down by the intestine, it is broken down instead by bacteria living in the gut. This causes gas to build up in the gut leading to bloating, flatulence, abdominal discomfort and loose motions. Symptoms only occur if you consume lactose and they tend to be worse the more lactose you take in. Symptoms usually start several hours after eating or drinking anything containing lactose.

Lactose intolerance is often inherited, and amongst peoples of some ethnicities, lactose intolerance is essentially considered normal in adulthood, particularly in those cultures where milk does not feature much in the adult diet. For example, lactose intolerance occurs in between 80–100% of East Asian people and up to 90% of people in some parts of Africa. Conversely, lactose intolerance is much less common in Northern Europe.

Sometimes lactose intolerance occurs as a result of another illness which has damaged the lining of the bowel. This is why people sometimes find that dairy products irritate their stomach for a few weeks following a bout of gastroenteritis. Diagnosis doesn’t usually require any tests. If you suspect you have lactose intolerance, you can try a 2 to 6 week trial of avoiding lactose during which time your symptoms should stop. After the trial, try eating or drinking something containing lactose and, if the symptoms recur, you can be confident that you are lactose intolerant. The difficulty is making sure that you avoid eating any lactose during the trial period because it can crop up unexpectedly in cakes, bread, snacks and even in the coating of some tablets.

Whilst food allergies, in general, are on the rise, lactose allergy remains far less common than lactose intolerance. As with other food allergies, some symptoms of lactose allergy occur several hours after consuming lactose, and these include abdominal pain, diarrhoea, eczema, tiredness, constipation or acid reflux. Because of this delay working out exactly what you’re allergic to can prove tricky but keeping a food diary usually helps. If you suspect you are reacting to lactose, this can again be assessed with an elimination diet. If an allergy is suspected in a child, you should consult a dietician before eliminating potentially important nutrients from their diet.

More alarming allergy symptoms can occur within seconds or minutes of eating lactose. These include rashes, swelling of the lips and tongue, difficulty breathing, and nasal itching and sneezing. At its most severe an allergic reaction can be life-threatening — so called anaphylaxis — and if you or someone you are with experiences difficulty breathing, or swelling around the face and mouth, you should seek urgent medical attention.

These more rapid reactions are controlled by something called ‘IgE’ which is an antibody in the blood. People experiencing symptoms suggestive of an ‘IgE-mediated reaction’ generally undergo testing for their allergy because it is important to work out exactly what they are allergic to and how strong their reaction to it is likely to be.
A blood test can be done looking for the specific IgE which is targeted against lactose or, alternatively, a doctor can perform a ‘skin-prick test’. During a skin-prick test a drop of the suspected allergen is put onto the skin of the arm, and then the skin is pricked through the drop with a needle. The skin is checked for a reaction about fifteen minutes later.

Antihistamines (hay fever tablets) usually settle mild symptoms if lactose is accidently consumed but those who suffer potentially life-threatening reactions should carry an injection of adrenaline with them to rapidly relieve the symptoms of an allergic reaction if it happens.

Lactose allergy is less common than lactose intolerance although some of their symptoms overlap. In both cases, conditions are often managed by simply avoiding lactose-containing food and drink. With numerous lactose-free alternatives to dairy products available in supermarkets, avoiding lactose does not typically present too much of a problem.