Skin Prick Testing

Skin prick testing is an investigation that allows the dermatologist to determine the cause of your reactions. Allergies can occur at any age and even overnight.

Skin prick testing is conducted by analysing the skin’s reaction to substances that may be causing the allergy.  Allergic reactions occur due to an inappropriate immune response (involving the body’s own immune system). The symptoms experienced, if the immediate part of the immune defence system is activated, include the development of wheals and intense itching. These are caused by the release of histamine and involve specific antibodies called IgE.

Common allergens causing an immediate allergic reaction include airborne allergens (e.g. pollens, house dust mite, animal dander, mould spores etc). Exposure to these allergens can cause symptoms similar to hay fever with runny eyes, nose and exacerbations of asthma.  However, they can also be triggered by foods (cows milk, egg, peanut, tree nuts, fish, shellfish etc). Their reactions can result in itching/swelling of the mouth and throat, itchy skin rashes, gastrointestinal effects (vomiting, diarrhoea, abdominal pain) and occasionally anaphylaxis.

The immediate types of allergic reactions are usually investigated with skin prick tests or blood tests looking for antibodies directed against specific allergens travelling in the blood. 

Who is Skin Prick Testing suitable for?

Skin prick testing is suitable for:

  • Patients who are experiencing the symptoms of an allergy, and who need to identify the trigger
  • Patients whose reactions suggest an allergic reaction, which require investigation to confirm a diagnosis

What is the Benefit of Skin Prick Testing?

Skin prick testing can indicate and confirm if an allergic reaction is related to any allergens that you may come into contact with, whether airborne, inhaled or ingested.

What is the process of Skin Prick Testing?

An average appointment will last 30-45 minutes. During your consultation a detailed clinical history will be taken which will allow us to decide on the most appropriate test(s) that you require before coming up with a detailed individual investigation, treatment and management plan.

Skin prick testing involves placing drops of solutions of the suspected allergen extract onto the skin of your forearm and then using a very fine lancet to prick through the drop into the skin. The procedure is well tolerated and causes minimal discomfort.  A positive test results in a small raised wheal. 

You should not take any anti-histamines, if possible, for 3-7 days before your appointment. Medicines that contain anti-histamines include certain cough medicines and anti-itch medications. If in doubt, please check with the clinic. Anti-histamines do not affect blood allergy testing and should not be discontinued in patients taking them for urticaria or angioedema. Ideally, you should also not apply any creams e.g. moisturisers to your forearms on the day of your appointment.

We can test you with a wide variety of allergens based on your history including:

  • Foods – if you suspect fresh fruits, vegetables, fish or seafood of causing symptoms, it is sometimes helpful to bring these along to the appointment to be used for skin prick testing as the commercially available solutions may be less reliable.
  • Spices
  • Animals
  • Pollens
  • Moulds
  • Dusts
  • Latex

Results are known within 10- 15 minutes. It is safe but has to be performed in a controlled clinical environment.


Allergy Blood (Specific IgE) Testing

This is another type of allergy testing that can help identify the cause of an allergic reaction and requires a blood test. It can be used alone or in conjunction with skin prick testing. Results take about 1-2 weeks and they are interpreted by the consultant in charge of your care.

Challenge Testing

If the test results are negative and don’t fit with the clinical history then it is sometimes necessary to perform direct food challenges.

A challenge test involves exposing you to a suspected allergen while you are in a safe, clinical setting in case you have a reaction. This is sometimes used to confirm (or refute) a food or drug allergy when skin and blood tests have proved inconclusive.

What is Desensitisation?

Desensitisation immunotherapy offers the possibility of curing certain types of allergy.  The programme involves carefully controlled repeated exposure to the allergen which can switch off the allergic immune response.  This can be achieved for aeroallergens (such as HDM, grass pollens, tree pollens, cat, dog and horse) and bee and wasp venom. 

Desensitisation immunotherapy is given either by injection or tablet form depending on the type of allergy you have.  The frequency of the treatments will vary but typically are delivered over the course of three to five years.

Desensitisation or immunotherapy uses allergen extracts to treat certain allergies e.g. hayfever / allergic rhinitis to grass or tree pollen, house dust mite. It is mainly indicated for individuals with symptoms not effectively controlled by optimum standard treatment i.e. usually regular long-acting non-sedating anti-histamines & intranasal corticosteroid sprays.

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