The body’s immune system has to constantly discriminate between many different unfamiliar molecules, some of which may be toxic substances while others are harmless components of food. An allergy results from an inappropriate immune response to such a substance (or allergen) such as dust, pollen or a component of food. An allergic reaction occurs as the body attempts to launch an attack against the foreign ‘invader’ perceived to be a threat to health. In such an attack, the body releases a substance called histamine, which dilates and increases the permeability of the small blood vessels. This results in a range of symptoms including local inflammation, sneezing, runny nose, itchy eyes and so on. These types of reactions may give rise to the so-called classic allergies: asthma, eczema, hay fever and urticaria (skin rash). These responses are called anaphylactic reactions and they vary widely in their severity. The most severe type of reaction (anaphylactic shock) may involve difficulty in breathing, a drop in blood pressure and ultimately heart failure and death.
Initial sensitisation to the allergen precedes an allergic reaction and this first exposure may not generate any perceivable symptoms. In fact initial sensitisation may result not from the direct exposure to an allergen but from exposure to dietary allergens during breastfeeding. Evidence suggests that this process, known as atopic sensitisation, can occur in exclusively breastfed infants whose mother’s breast milk contains dietary allergens. For example, a Finnish study reported that a maternal diet rich in saturated fat during breastfeeding might be a risk factor underlying the later development of allergies (Hoppu et al., 2000). The same research group later reported that breast milk rich in saturated fat and low in omega-3 fatty acids might be a risk factor for eczema (Hoppu et al., 2005). While numerous studies now show that breastfeeding can protect against the development of allergies, and the majority of studies are strongly in favour of breastfeeding, it may be prudent to avoid suspected allergens in the diet while breastfeeding especially if allergies such as asthma, eczema and hay fever run in the family.
Allergies are now so common in the UK, affecting around one in three people, that the increasing occurrence is referred to by some as an epidemic (Royal College of Physicians, 2003). The UK is one of the top countries in the world for the highest incidence of allergy, especially asthma. Millions of adults in the UK are affected by at least one allergy and numbers continue to rise (Allergy UK, 2013). Each year the number of allergy sufferers increases by five per cent, half of all affected being children, and by 2015, 50 per cent Europeans will suffer from an allergy (EFA, 2011).
Food allergy is increasingly widespread and the most common of these is cow’s milk allergy, affecting around two per cent of all infants under the age of one. Symptoms include excessive mucus production resulting in a runny nose and blocked ears. More serious symptoms include asthma, eczema, colic, diarrhoea and vomiting.
Asthma is a chronic, inflammatory lung disease characterised by recurrent breathing problems. Asthma is a common condition in the UK; 5.4 million people are currently receiving treatment for asthma (NHS Choices, 2012b). That is one in every 12 adults and one in every 11 children. The number of children with asthma has risen steeply since the 1970s when just one in 50 children had asthma. Asthma prevalence is thought to have plateaued since the late 1990s, although the UK still has some of the highest rates in Europe and on average three people a day die from asthma (Asthma UK, 2013).
During an asthma attack, the lining of the airways becomes inflamed and the airways become narrower causing the characteristic symptoms of asthma: coughing, wheezing, difficulty in breathing and tightness across the chest. Asthma can start at any age and the causes are thought to include a combination of factors including a genetic predisposition (asthma in the family), diet and environmental triggers such as cigarette smoke, chemicals and dust mites.
As stated previously, allergies tend to run in families, so asthma, eczema or hay fever in some family members may increase the risk of others developing the same or another allergy. But a genetic predisposition is not the only cause, as stated asthma is caused by a combination of factors. In the past, the rise in childhood asthma has been attributed to an increase in air pollution. However, this seems unlikely as many of the most polluted countries in the world, such as China, have low rates of asthma, whereas countries with very good air quality, such as New Zealand, have high rates of asthma (ISAAC, 1998). The ‘hygiene hypothesis’ has gained popularity as a causal factor for the increase in asthma. This hypothesis blames the increasing asthma rates on the extreme levels of cleanliness found in many homes. Increased hygiene means that our immune systems are being challenged less and less. It has been suggested that this causes us to overreact to allergens such as dust mites.
Food allergy is frequently underestimated in association with asthma despite the fact that food allergy and asthma frequently co-exist. Children with food allergy are more than two to four times as likely to have other atopic conditions such as asthma, eczema or respiratory allergy compared to children without food allergies (Kewalramani and Bollinger, 2010). Furthermore, food allergy has been shown to trigger or exacerbate broncho-obstruction in two to 8.5 per cent of children with asthma (Baena-Cagnani and Teijeiro, 2001). Food allergies may be responsible for around five per cent of all asthma cases (James et al., 1994) and as cow’s milk is a primary cause of food allergies, it may therefore be useful to consider the possibility of cow’s milk allergy in the treatment of asthma.
Eczema (also known as atopic dermatitis) is a condition that causes the skin to become itchy, red, dry and cracked. It is a long-term, chronic condition. Eczema can vary in severity and most people are only mildly affected but severe symptoms can include cracked, sore and bleeding skin. Severe eczema can have a significant impact on daily life. The number of people diagnosed with atopic eczema has increased in recent years and currently, about one in five children and one in 12 adults in the UK have eczema (NHS Choices, 2012b; National Eczema Society 2013).
Cow’s milk allergy is a risk factor for many allergic conditions including asthma and eczema (Saarinen, 2005). There is an increasing amount of interest in the role of the diet in the development of eczema. In recent years, the links between certain foods and eczema has become better understood. Eczema can be caused by several environmental factors including dust mites, grasses and pollens, stress and certain foods. Eczema usually starts when a baby is around six months old and in about 10 per cent of cases it is triggered by foods including milk, eggs, citrus fruit, chocolate, peanuts and colourings (NHS Choices, 2013c). The most common food triggers are cow’smilk and eggs, but many other foods including soya, wheat, fish and nuts can act as triggers (National Eczema Society 2013a). So, when treating eczema, cow’s milk allergy should be considered.
Hay fever (seasonal allergic rhinitis) is an allergic reaction to grass or hay pollens. A minority of cases may be caused by later flowering weeds or fungal spores, and some research suggests pollution can worsen symptoms. In response to exposure to pollen, the immune system releases histamine which gives rise to a range of symptoms including a runny nose, sneezing and itchy eyes and throat. Hay fever is often regarded as a trivial problem but it can severely affect people's quality of life, disturbing sleep, impairing daytime concentration, it causes people to miss work or school and has been shown to affect school exam results (Allergy UK, 2012).
Hay fever is one of the most common allergic conditions that affects up to one in five people at some point in their life. Hay fever is more likely if there is a family history of allergies, particularly asthma or eczema (NHS Choices, 2011). Some evidence suggests that altering the diet can help some people with asthma and allergic rhinitis (Ogle and Bullock, 1980). However, the effects of diet on hay fever symptoms have not yet been well studied. As cow’s milk allergy is linked to other allergic reactions (see above) it may be sensible to consider avoiding all dairy in order to combat hay fever symptoms.
As stated above, cow’s milk-induced gastrointestinal bleeding as an allergic response is a well-recognised cause of rectal bleeding in infancy (Willetts et al., 1999). One of the main causes of gastrointestinal bleeding is dietary protein allergy, the most common cause of which is cow’s milk protein (casein). Gastrointestinal bleeding from cow’s milk allergy often occurs in such small quantities that the blood loss is not detected visually, but over prolonged time these losses can cause iron-deficiency anaemia in children. Intestinal blood loss associated with cow’s milk consumption during infancy affects about 40 per cent of otherwise healthy infants (Ziegler et al., 2011). In one trial of 52 infants, 31 of whom had been breastfed, and 21 fed formulas up to the age of 168 days of age, the introduction of cow’s milk (rather than formula milk) was associated with an increased blood loss from the intestinal tract and a nutritionally important loss of iron (Ziegler et al., 1990).
Frank Oski, former paediatrics director at Johns Hopkins School of Medicine, estimates that half the iron-deficiency in infants in the US results from cow’s milk-induced gastrointestinal bleeding (Oski, 1996). This represents a staggering figure since more than 15 per cent of US infants under the age of two suffer from iron-deficiency anaemia.
The only reliable treatment for cow’s milk allergy is to avoid all cow’s milk and dairy products including: milk, milk powder, milk drinks, cheese, butter, margarine, yogurt, cream and ice cream. Also products with hidden milk content should be avoided. Food labels that list any of the following ingredients also contain some cow’s milk or products in them: casein, caseinates, hydrolysed casein, skimmed milk, skimmed milk powder, milk solids, non-fat milk, whey, whey syrup sweetener, milk sugar solids. These ingredients can be difficult to avoid as they are commonly used in the production of bread, processed cereals, instant soups, margarine, salad dressings, sweets, cake mix and even crisps. It can seem a daunting prospect having to read the ingredients labels but most supermarkets now produce ‘free-from’ lists of products and many supermarkets also have their own label free-from range. There are even iPhone apps available now to help you identify ingredients by scanning the product bar code. Soya ice creams, spreads and yoghurts and dairy-free cheeses are just some examples. Calcium-enriched soya, rice and oat milks can be used as alternatives to cow’s milk. (For other gastrointestinal problems associated with cow’s milk see Lactose intolerance.)