Allergy & Eczema

Terminology about food reactions can be confusing, since reactions with very different causes are often referred to using the same words. The main types are:

• Immediate allergic reactions occur within minutes to hours after eating a food and involve an immune molecule called IgE. These are considered "true allergies." Symptoms can include hives, vomiting, or lip swelling. Anaphylaxis is the most severe type.
• Delayed reactions begin hours to days after ingesting a food and are caused by the immune system, but not by IgE. Examples include coeliac disease and cow's milk protein intolerance/allergy. These do not cause anaphylaxis.
• Intolerances occur when there is a problem digesting a food, and do not involve the immune system. An example is lactose intolerance. Allergy testing is not useful for intolerances.

For more detail, refer to this ASCIA page on food intolerance.

Small amounts of mucus in the stool of a well infant is normal. Large amounts of mucus and/or any blood would make us think about other causes, such as infection. Mucusy stool with fresh blood in a healthy, thriving baby is commonly due to a delayed immune reaction to a food protein (often cow's milk). This condition does not cause immediate symptoms like hives or anaphylaxis. A thorough assessment by a GP or paediatrician is always warranted.

Lactose is a sugar found in milk, and its digestion requires an enzyme called lactase. Lactose intolerance occurs when there is not enough lactase, leading to tummy pain, bloating and diarrhoea. In infants and young children, lactose intolerance is usually a temporary problem after a viral illness like gastroenteritis, and resolves within weeks. It is extremely rare for babies to be born with lactose intolerance.

The most important part of allergy diagnosis is the history. If an immediate-type allergy is suspected, a skin prick test, blood test, or oral food challenge can help confirm the diagnosis. A skin prick test involves pricking the skin with food extracts and looking for a wheal (swelling). Blood tests measure IgE antibodies targeting specific foods. An oral food challenge involves eating small amounts of a food under close medical supervision. Interpreting allergy tests requires careful consideration — a positive test does not always mean a clinical allergy.

Common food allergens include cow's milk, egg, soy, tree nuts, peanut, sesame, wheat, fish and shellfish. Food allergens should be introduced from around 6–12 months of age along with other solids. Each allergen should be introduced by itself first, and during the day, so that any reaction can be detected. Peanut and tree nuts should always be given crushed or as a paste. Once introduced, try to keep giving allergenic foods regularly (e.g. twice a week) to maintain tolerance.

For further information, see preventallergies.org.au.

A good rule of thumb for children with eczema is to keep the skin cool, clean and moisturised:

• Cool: Avoid hot baths, showers or hot itchy clothing.
• Clean: Wash daily to remove bacteria; bleach baths can be considered if needed.
• Moisturised: Apply moisturiser twice daily, even when skin appears healthy. Avoid products containing fragrances or food substances (e.g. almond oil, coconut oil, milk), as these can increase the risk of developing an allergy to those foods — especially in infants with eczema.

Eczema can flare in response to many triggers, including food allergens, dustmites, chemicals like chlorine or soap, and after viral illness. Although rare, some people have reported a flare after a vaccine. Maintaining excellent baseline skin care helps minimise flares while allowing more flexibility in diet and lifestyle.

Topical steroids are safe to use in children with eczema and should be applied in ample amounts to the affected areas — not sparingly. They can be stopped when the skin has healed, with regular moisturisers continued. Side effects are rare and more likely only with long-term use of very strong steroids over large skin areas.

There are increasing concerns about 'topical steroid withdrawal'. A British dermatology expert group has released a statement acknowledging that more needs to be learnt, but emphasising that topical steroids should continue to be used as needed.

Hayfever (allergic rhinitis) is an allergic reaction to environmental substances such as house dust mite, pollens, grasses and moulds. It is uncommon under 2 years of age and gradually becomes more common, affecting about 1 in 3 adolescents. Its impacts are often underrecognised — it can significantly impact sleep quality, which in turn affects daytime function including attention and behaviour.

Hayfever can be diagnosed based on symptoms and examination findings. Testing is not needed to confirm the diagnosis but can help identify specific triggers, for example by skin prick testing.

• House dust mite allergy factsheet — Sydney Children's Hospital Network
• ASCIA advice on reducing allergen exposure