23 Mar 2023

Everything You Should Know About Skin Prick Test

Allergies are quite common and a skin prick test allows to identify tiny amounts of allergens on the body. This provokes a localised reaction which can help identify what allergies are present, especially if the allergen is uncommon or specific.

If you think that you need allergy testing then the first thing to do is to ring us for an appointment with a Consultant Immunologist. Before you ring us, try to pinpoint when your symptoms began because you will be asked about that when you have your consultation with the specialist, as well as with some information about any medication you have been on and the symptoms you are experiencing.

When you come for an appointment you will be seen by our consultant who will take details of your clinical and medical history. They will ask you several questions about your general health, your diet, your work and home environments and of course your symptoms. These is necessary to try to work out what is triggering allergic reactions in you. It will also help in deciding what treatment might be necessary. As there are several types of allergy testing our expert may discuss various types with you explaining why one would be better than another method.

What happens with a skin prick test?

This test is the most common way for a doctor to find out the kind of allergy you are suffering from. During testing, a few drops of a solution that contains an allergen will be introduced onto the skin of your arm. If the allergy is thought to be a food allergy you might even have a piece of fresh food attached to your arm to gauge your reaction.

Next, the allergist will make a small prick on the skin so that the allergen can get through to your tissue. This small prick or scratch is very rarely painful and very rarely causes bleeding. You may have several of these pinpricks or scratches at once, to test for various allergens.

If there is an allergy present, then your skin will usually react within half an hour with a white bump raised from the skin and surrounded by a smaller circle of red skin that itches.

Do I know if I should have hey skin prick test?

The demonstration of atopy is the aim of conducting this test. Atopy is actually an immune response that overreacts to an environmental factor and will often have a very strong genetic component. Some of the most common manifestations of allergy will be eczema, asthma or rhinitis (hay fever).

Examining the test results will help in the management of those patients with hay fever or with asthma for example, in planning desensitisation to the allergens causing the reaction, removal of a family pet or carpets or maybe avoiding certain food or drink. It is also useful for patients who have wasp and bee stings as well as acute urticaria especially if they're being considered for immunotherapy.

In some conditions, conducting this test is not very helpful such as in chronic urticaria and angioedema, atopic dermatitis, intolerance of food types, rashes that are non-specific and dermatitis herpetiformis.

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How Should I prepare for my pin prick skin test?

The most helpful thing you can do before you come for a test is to gather information for the specialist about your allergies, when they started and what sort of symptoms you are having. If you have been taking antihistamines don't take them before you come for the test. Let your allergist have the details of any antihistamine you've been taking and depending how your antihistamine works you may need to discontinue it for over a week. This will include allergy or cold medications that contain antihistamine in combination with other ingredients.

There are some other medications that might influence your skin prick test results. Discuss them with your allergist beforehand so that you know whether or not you should take them before you come for your test. On the day that you come for your test to make sure that you don't use any body lotions or that you don't spray any perfume or aftershave on the area that the test will be performed on.

It is possible that you may react positively to an allergen but never experience symptoms for that allergy. A false negative or a false positive are also possible. Having a false negative is a dangerous situation because there is no indication of the substance that is causing your allergy and you will not have definitive information about what to avoid. Even so, it is always a good idea for you to have a test because if substances that are triggering your allergies are identified, you and your doctor can work together to help with relief of your symptoms.

What should I expect when I have my test?

Before you start with the testing, a full medical history will be taken as well as details of the symptoms you've been having and your information about your allergy triggers. The doctor will then use the information you give to decide which allergens should be used in your test. The test may involve three or four substances being checked or in extreme cases as many as forty.

The pin prick test will usually be done on the skin on the inside of your arm or it may be done on your back. Typically a doctor will be the one to administer your test and then the doctor will come to assess your reaction. The testing procedure as well as the interpretation of results will usually take less than an hour although this very much depends on how many allergens have been used in testing.

Skin Prick Test Procedure

First the skin in the area to be tested will be thoroughly cleansed with alcohol.
Next the doctor will make some marks on your skin which will then be used to track the different allergens you are introduced to and any skin reaction there is.
Each allergen will be placed on your skin in the form of a small droplet.
Under each of the droplets the doctor will lightly prick or scrape the skin so that the allergen can seep through. This is not painful although some people may find they feel a slight irritation.
Once this part of the test has been completed you will need to wait to see if any reaction is observed and this would usually be seen after around 20 minutes. At that point if you are testing allergic to any of the substances your skin will develop an itchy red lump and the area where the allergen was introduced will look quite like a mosquito bite inside a reddish ring.
How you have reacted will be measured and evaluated and the bumps that have come up on your skin will usually go down again over the next few hours.

This type of test can be carried out on anyone, even an infant, as long as they are more than six months old. The testing is widely in use and generally very safe. In very rare cases, this testing might trigger an allergic reaction that is more severe although this is often predictable because it is most likely to happen in a person who has a past history of reacting severely.

It is also more common for this to happen during food allergy testing. If this rare occurrence did happen you would not need to worry because your doctor would be prepared for all eventualities and would be able to treat you for your reaction.

Is skin prick testing very accurate?

It is rare to get a false negative result with this type of test. If you do get a negative result this will almost always indicate that there is no allergy to any foodstuff that you have been tested for.

In fifty to sixty percent of cases however there might be a falsely positive result which might make it look as though you are allergic when in actual fact you are not. However there is no need to worry about false positives allergists will be using other tests to help them verify your results. These will include blood tests.

This is not something you need to worry about, however. Allergists will verify results with other tests. These include blood tests like (enzyme-linked immunosorbent assay (ELISA), or with an oral food challenge.

Someone who is trained in assessing for allergies will be using the best test for your particular condition after they have examined, in detail, your full medical history and the symptoms you have reported. This will ensure that they find exactly the right treatment for you.

Our consultants all very expert in the field with many years of successfully testing adults and children for allergic reactions. Give us a ring too make an appointment or book yourself an appointment online.

Concerned about any of the issues raised in this article? It's well worth undergoing a full body health screening to check for underlying issues, with 4 GP appointments included in all Advanced and Elite MOTS throughout 2023.