Allergy testing

Allergies are very common and affect the vast majority of people in the UK. They are a hypersensitive reaction to a substance, object, medicine, chemical or food which triggers a range of symptoms including a skin rash.

If your GP suspects that your skin condition is caused by an allergy then you will be referred for allergy testing. There are 3 types of tests which are:

  • Blood test
  • Patch test
  • Skin prick test

Blood test

Most people are familiar with blood tests, having undergone them at some point in their lives. A small sample of your blood is removed and then sent to a laboratory for analysis. They will look at electrolyte levels, presence of antibodies, thyroxine levels etc.

The presence of any of these will help support your GP’s or dermatologist’s diagnosis.

Patch test

Patch testing is a popular form of allergy testing in which small amounts of suspected allergens, e.g. dust are spread onto non-allergenic metal discs. These discs are then taped onto your skin, usually your back. They are left in place for up to 48 hours.

They are then removed and your skin checked to see if there have been any reactions. This is repeated 48 hours later.

This test is usually carried out in a dermatology department at a general hospital. It is performed as part of a series of diagnostic procedures for contact dermatitis.

Skin prick test

Your skin is pricked with a needle containing a tiny amount of a suspected allergen. If the skin becomes red, swollen and itchy then that is a clear indication that there has been an allergic reaction.

This is a safe test: only a tiny amount of the allergen is used which will not provoke a severe reaction. This makes it suitable for all age groups, from the very young to the very old.

But it is not recommended for anyone who has experienced severe allergic reactions.

The skin prick test is usually the first test to be carried out followed by the other two. You may have a very good idea of what is causing your skin allergy but testing is still required to confirm an accurate diagnosis.