What causes allergies?
An allergy is when the immune system responds to an allergen such as food or pollen, as if it is a harmful substance. Your body responds by producing antibodies to help remove the allergens from your system. This results in the chemical ‘histamine’ to be released and it is that the causes symptoms that we call an allergic reaction.
How are allergies diagnosed?
There are a number of ways to determine allergies but a skin prick test is by far the common as it gives fast and accurate results. Skin prick testing works by exposing your child’s skin to many different substances, or allergens, at one time and then being observed for signs of an allergic reaction. The results will determine if a particular allergen is causing your child’s symptoms when that allergen is touched, eaten, or breathed in.
What can allergies can be diagnosed with a skin prick test?
We can perform skin prick tests for a range of foods such as milk, eggs, soya, nuts, seafood and a range of meat. We can also test for a wide range of aeroallergens, for example grass and tree pollen and house dust mites. You can also bring a specific food from home if you are concerned your child might be allergic to it. It shouldn’t be cross contaminated with any other food and if it is food that is usually cooked you should bring a raw and cooked sample.
How is skin prick testing done?
One of our specialist paediatric nurses will place a small amount of allergen is on your child’s forearm. Several allergens can be tested at one time. The nurse will then wipe away the drop. The skin under the drop is then pricked to let the allergen get below the surface of the skin. It may be a little uncomfortable but it won’t be painful. If we perform a test with the food you have brought with you, we will prick a piece of food with a lancet and then immediately prick your child’s skin with it. This method is called “prick to prick testing”. We will make a different mark on your child’s skin with a washable pen for each test. This means we can identify the different allergen tests.
A positive reaction – the area where the skin has pricked becomes red and itchy. The raised swelling called a “wheal” and is surrounded by a red area. This will fade after a few hours. This means your child is likely to be allergic to the substance.
A negative reaction – the skin where the drop of allergen has been pricked remains normal. This means your child is less likely to be allergic to the substance.
Once the test is complete, your skin will be cleaned and cream added to alleviate any itching. Any reaction usually disappears within 30 minutes to a few hours.
Are there any alternatives to a skin prick test?
A blood test can be used to measure your child’s allergic response to a specific allergen. However, skin prick testing is quicker than a blood test.