A strong link between asthma and eczema is now globally recognised, but the role of food in easing both conditions is yet to be determined. We investigate how avoiding certain foods, especially those with sulfites, may help
What is asthma?
Asthma is a chronic disease of the airways (the tubes leading to the lungs), which affects one in six adults and one in four children. When asthmatics are exposed to certain triggers their airways become inflamed and narrowed, restricting airflow to the lungs. This causes symptoms such as wheezing, coughing, chest tightness and difficulty breathing. Asthma can’t be cured but it can be controlled so that sufferers can live active lives and have few and infrequent symptoms.
What is eczema?
Eczema is an inflammatory condition of the skin, which varies from very mild to severe. Mild eczema often results in dry, hot and itchy skin, while severe eczema is characterised by broken, raw and bleeding skin. Eczema can occur anywhere on the body, but for both adults and children the most common places are the face, neck, elbows, knees and ankles. Infants that are affected often show signs on their foreheads, cheeks, forearms, legs, scalp and neck.
Finding the link between asthma and eczema
In 2006, Scottish researchers discovered a genetic mutation in the skin of people who have eczema and asthma. The gene, called filaggrin, helps form the skin’s outer protective layer, which is made up of dead cells that are collapsed together into a continuous protein sheath that lets water in and invaders, such as bacteria, out. A mutation in the gene stops the formation of this outer protective layer and predisposes the individual to eczema and concomitant asthma, suggesting a possible role in disease transition.
More recently, Australian researchers discovered that those who have childhood eczema are twice as likely to develop asthma, further suggesting a more aggressive treatment of childhood eczema may be an important step in preventing asthma later in life.
The role of food in asthma and eczema
Food triggers asthma in less than five per cent of asthmatics but it plays a far more significant role in the development of eczema.
Australian research has found that approximately half of all children with eczema are sensitive to one or more foods.
Food can trigger asthma and eczema as part of either an allergic reaction or chemical intolerance to food, food additives or food chemicals. During an allergic response, the body’s immune system overreacts to a substance (allergen) that most people find harmless. Being exposed to this allergen may cause an immediate reaction (swelling, redness and a rash) or delayed reaction (increased itching and eczema and/or abdominal pain and diarrhoea). Swelling in the nose, eyes, lungs, airways and skin can also occur, inducing asthma or making it worse.
Eating for asthma and eczema
There is no diet for asthma or eczema. However, if food is thought to be a trigger, removing any problem foods from the diet can help. A doctor or Accredited Practising Dietitian can put you on a food challenge that eliminates suspected problem foods for two weeks, then reintroduces them one at a time. If there is an adverse reaction, you will then be advised to avoid these foods.
Possible food triggers
Peanuts, tree nuts, sesame seeds, fish, shellfish, dairy products, eggs as well as food flavourings and colourings.
Cow’s milk, eggs, soybeans, wheat, fish, peanuts and tree nuts.
Sulfites and asthma
What are sulphites?
Sulfites are normal products of metabolism and are naturally present in the body. They can also be produced by microorganisms and are present in small quantities in many foods, even where none have been added.
Role in asthma
Sulfites are known to be safe, however a small number of people can have an allergy-like reaction to them, and these people are mainly asthmatics. For asthmatics, sulfites can provoke asthma and other symptoms of an allergic reaction such as skin rashes and irritations.
These include dried fruits or vegetables, wine and beer, fruit juice, soft drinks and delicatessen meats.
Why are they added to food?
Sulfites act as a preservative by slowing down the growth of microorganisms, which could otherwise spoil foods. They may also be used as processing aids such as for sterilising bottles prior to packaging food or drink.
Identifying sulphites in food
People with asthma should be aware of which foods contain sulfites. Check the food’s ingredient list as sulfites must be shown under their class name, followed by the additive’s specific name or code number (220 to 228). For example, the ingredient list may state sulfites as ‘preservative (223)’. Foods containing 10 milligrams per kilogram or more of added sulfites must be labelled as ‘containing sulfites’. This is the level that may trigger asthma attacks in some asthmatics.
Asthma and Gastro-Oesophageal Reflux Disease (GORD)
Animal research released in July this year found that inhaling tiny amounts of stomach fluid back into the oesophagus can produce changes in the immune system. This can then drive the development of asthma. This might explain why studies have found GORD to affect 50–90 per cent of asthma sufferers.
Antibiotics and infants
Infants who receive a course of antibiotics during the first six months of life are 2.5 times more likely to develop asthma by the age of seven, according to a Henry Ford Health System study. Before giving your child antibiotics, ask if the illness can be treated without them.
Breastfeeding and asthma risk
There is evidence to suggest that breastfeeding your child for at least six months reduces their likelihood of developing asthma. Early weaning is believed to play a role in asthma development.
Breastfeeding and eczema risk
Breastfeeding is recommended for infants at risk of developing eczema. It provides nutritional, immunological and physiological nourishment.