What is an allergy?
An allergy develops when the body’s immune system overreacts to a substance that is not normally harmful e.g. grass pollen. In allergic reactions the body produces powerful chemicals such as histamine. These chemicals can cause unpleasant symptoms.
People can have allergies to almost anything, from animals, bee and wasp stings to grasses or even chocolate. The substances that cause reactions are called allergens.
Symptoms include:
- Urge to sneeze, runny or blocked nose causing breathing difficulty (rhinitis).
- Itching, reddening, watering, swelling of the eyes (conjunctivitis).
- Asthma causing coughing, wheezing and occasionally breathing difficulty.
- Nettle-like rash or eczema may occur on direct skin contact with some inhalant allergens.
What is a skin prick test?
A skin prick test assists in the diagnosis of allergies. The health care professional performing your test will prick gently through a drop of allergen extract placed on the surface of the arm. If you are allergic to the allergen you will have a small, itchy swelling and reddening of the skin after 10-15 minutes.
Why am I having a skin prick test done?
Your doctor has decided that you might have an allergy, so you will be asked when your symptoms are most obvious, such as inside the home, outdoors, night-time etc. From that information the doctor can choose which allergens you need testing for.
What must I do before the skin prick test?
You should not take any antihistamines or cough medicines for 7 days before attending your skin prick test clinic; this is because these medicines interfere with the body’s reaction to the skin prick test and could suppress your test results. Please speak to a pharmacist if you are unsure of the ingredients in any medicine you are currently taking.
Performing a skin prick test
- The healthcare professional will rest your arm near the edge of a table. Using a skin marking pen, they will mark and code the inside of the forearm, either onto some tape or directly onto the skin.
- The healthcare professional will then apply one drop of each allergen solution on to the skin next to its code number.
- They will then prick your skin through the drop using a special lancet. A constant pressure will be kept for 1 second then the lancet will be removed. Most people do not feel anything other than a slight pressure.
- Your arm will then be dried.
- You will then be instructed to wait for 15 – 20 minutes. However, the reactions will be observed at regular intervals to see how they progress.
- After the time has elapsed, the healthcare professional will read the reactions. They may draw around any reactions with a special pen and measure them.
The reactions disappear after 2 to 3 hours. The healthcare professional may apply cream to stop any itchiness caused by the reactions.
You may resume your medication unless the doctor advises otherwise.