Paediatric Allergy

Allergy Testing at Paediatrics Ballarat

Allergy testing is undertaken by allergy nurses Mandy Wilson or Lauren Malone and A/Prof Shabna Rajapaksa or Dr Nelu Jayawardena at Paediatrics Ballarat. During the consultation the Paediatrician and Nurse will decide whether allergy testing is indicated in your child.

Allergy testing (usually either Skin Prick Testing or RAST blood tests) helps to identify accurately which allergens a patient is sensitive to, so that appropriate avoidance advice can be given. It is important to note that allergy test results are only meaningful if considered together with the medical history and testing will not be relevant in all cases.

In the case of skin prick test being performed during the appointment, please prepare by doing the
following:

• Withhold all antihistamine medications (Zyrtec, Claratyne, Phenergan, Telfast etc) and antihistamine like medications such as teething mixtures, cough, and cold medications (Dimetapp, Benadryl, Demazin etc) for 7 days prior to your child’s allergy appointment. These medications may interfere with test results.
• Please continue all topical application of eczema treatment (including steroid ointments & creams), nasal steroids and asthma medications as applicable.
• Allergy testing cannot be performed until 6 weeks after anaphylaxis is experienced/ Epipen/Anapen is administered.

Which Allergens would be tested for?

Skin Prick Testing can confirm some suspected allergies to foods, but generally only in the acute, immediate, and reproducible types of reactions (IgE mediated reactions). It is not useful for delayed reactions (> 2 hours) such as diarrhoea and eczema (non-IgE mediated reactions). In children with hay fever or asthma, allergy testing may include house dust mite, cat and dog dander (perhaps other animals if contact occurs), mould spores and pollen from relevant grasses, weeds or trees.

It is generally not feasible to test for preservatives and additives in either foods or cosmetics. Testing for allergies to medications is a more complex process and may eventually involve a medication challenge in hospital, rather than a blood or skin prick test.

Skin Prick Testing (SPT)

SPT is most commonly performed on the back, although the forearm is sometimes used. A drop of commercially-produced allergen is introduced into the skin with a sterile device. With a positive test, a small mosquito-like lump will appear at the site of testing over 15-20 minutes.

Local itch and swelling normally subsides within 1-2 hours. More prolonged or severe swelling may be treated with an oral antihistamine, topical corticosteroids cream and an ice-pack. SPT is slightly uncomfortable, but is usually well tolerated, even by young children. Your child should be reassured that this procedure does not hurt. We are more than happy to demonstrate on mum/dad/siblings to decrease anxiety.

Once the SPT results are available (mostly within 20 minutes), your doctor will interpret and discuss the results with you at the same appointment. Blood tests are however done off site and the result will only be available a few days later.

SPT at Paediatrics Ballarat is performed with the same technique, reagents and equipment as the Royal Children’s Hospital and in accordance with ASCIA (Australian Society for Clinical Immunology and Allergy) guidelines. Some of the extracts and pricking instruments used are not TGA (Therapeutic Goods Administration) approved. There will be opportunity for further questions and discussion at the time of the appointment.

Atopy Patch Testing, which may apply in some of these cases, is not offered by our clinic, but in select cases a referral to a sub-specialist may be relevant. Testing for allergies to medications is a more complex process and may eventually involve a challenge in hospital, rather than a blood or skin prick test.