There are three main methods of reliable allergy testing available which carry a high degree of sensitivity and specificity. Skin Prick Allergy Testing and IgE specific blood testing are used to identify allergies to a wide range of airborne allergens and foods. Patch testing is used specifically to identify the contact allergic trigger in a condition called contact dermatitis.
Skin prick allergy testing is regarded as the gold standard allergy testing method as it carries a number of advantages over IgE specific blood testing. It is therefore used in Allergy Ireland and other major centres such as Crumlin Children's Hospital Ireland (CHI).
Skin Prick Allergy Testing
Skin prick testing is a safe, fast and virtually painless investigation that identifies whether allergic sensitivities are present in an individual. It can be used to test for a wide range of airborne allergens and food substances and the results are available within 15 minutes. At Allergy Ireland allergy testing is immediately followed by consultation with one of our doctors who will accurately interpret the results and tailor a management plan.
Skin prick allergy testing involves placing small droplets of allergens onto the skin and then introducing a tiny amount of each allergen into the skin. If allergic sensitivity is present, then a temporary bump called a wheal will form on the skin and the surrounding skin will become red. The results are available within 15 minutes and ready for review by the doctor. It is vital that this result is interpreted there and then by a specialist doctor. It’s easy to perform an allergy test, the skill lies in interpreting the result in the context of the patient's symptoms. Sometimes there is no link.
In cases where a food challenge is under consideration then sometimes both skin prick allergy testing and IgE specific bloods tests are sometimes carried out. This depends on the specific case history.
The following allergens can be tested:
- Inhalant Allergens: House Dust Mite, Grass Pollen, Tree Pollens, Silver Birch Pollen, Feathers, Animal Dander (cat/dog/horse/rabbit) and Household Mould Spores (alternata & cladasporium).
- Foods: Milk, Egg, Wheat, Soya, Potato, Tomato, Orange, Strawberry, Kiwi and Chocolate (Cocoa).
- Nuts/Seeds (where appropriate): Peanuts, Almonds, Walnuts, Hazelnuts, Brazil nuts, Pine nut, Pistachio nut, Pecan nut, Cashew nut, Chestnut, Sesame seed, Sunflower seed.
- Fish/Shellfish (where appropriate): Cod, Mackerel, Salmon, Tuna, Trout, Hake, Shrimp, Lobster, Crab, Clam, Mussels and Scallops.
Please Note: If you or your doctor would like you to be tested for something not on our list please contact us by e-mail. For example, if you bring a small sliver of fresh food then that can be tested directly. This is usually done for specific fish you suspect you may have reacted to if it is not available in allergy extract form. PLEASE DO NOT TURN UP WITH A SHOPPING TROLLEY FULL OF THINGS YOU WANT TO BE TESTED FOR (it has happened!).
A positive result is measured in millimetres of central wheal and outer flare (redness of skin). There are positive (histamine) and negative (saline) controls to ensure the accuracy of test result.
With inhalant allergens (such as dust mite, pollens, animal hair) the size of the wheal and flare is important but does not always reflect the symptoms. For example a patient will occasionally show a very large wheal and flare (say to dust mites) but not show many symptoms. Equally a relatively small reaction (say to cat hair) in someone only recently exposed to cats is usually very important as within a year of continuous exposure the allergic reaction will probably have increased significantly (as will the patient’s symptoms).
It’s easy to perform an allergy test, the skill lies in interpreting the result in the context of the patient's symptoms. Sometimes there is no link.
Patch Testing is used specifically to test for allergic triggers in a condition called Contact Dermatitis.
Contact Dermatitis occurs when the skin reacts to a substance which it has been in direct contact with resulting in a red, itchy rash. The rash occurs in the same distribution as the area of contact. The commonly occurs on the hands as a result of occupational exposures such as Latex or Rubber containing gloves. It is found more commonly in women than men, primarily due to nickel found in some jewellery and to acrylate allergy associated with nail cosmetics. Contact dermatitis is particularly prevalent in metal workers, cleaners, painters, hairdressers and health care workers.
Patch Testing uses three strips of test patches containing 36 different substances. These substances tested for are the common chemicals in our daily environment and workplaces that most frequently cause skin reactions. They include fragrances, cosmetics, hair dye, dental metals, suncream, lanolin and adhesives. The patches are applied to the skin and then removed and examined by one of our doctors 2-3 days later to give us our results.