At your first appointment, the consultant will take a history from you about the type of symptoms you have and their severity. It will be helpful if you mention anything you think you may be reacting to.
Following this, the consultant may either decide to give you a blood test or a pin prick test for a variety of allergens to assess what is causing your symptoms.
The blood test measures antibodies, for example to peanuts or latex. These are produced when you come into contact with an allergy trigger and are your body’s defensive response.
If allergy testing is considered appropriate, you will be given an appointment for this. The test involves pricking microscopic amounts of allergens through the skin, usually on the forearm, and checking some minutes later to see whether the skin has reacted to any of them. You will be tested for your response to allergens such as feathers, dust mite, pet hairs, nuts or various types of pollen.
If you are taking antihistamines to treat your symptoms, you will need to stop them temporarily as they can prevent the skin from reacting to the allergens that are applied and will interfere with the results of the test.
The itchy reactions on the test site usually resolve within an hour or so after the procedure.
The body’s immune system itself causes the allergic response when it over-reacts to something it perceives as a threat, such as dust, mould or pollen. The antibodies it creates are directly responsible for the symptoms.
Patients with asthma, atopic eczema, allergic rhinitis (hay fever) and allergic conjunctivitis are all suffering from type I allergies, i.e. an abnormal reaction to substances naturally present in the environment. These allergies usually occur very quickly on exposure to the antigen and are often driven by genetic factors.
The other most common family of allergies is type IV, and this involves a delayed reaction to the substance that stimulates it. It is caused by a reaction in the cells rather than the production of antibodies in the blood.
To assess allergies in this category, dermatologists offer patch testing, in which they attach suspected irritants in small containers to the patient’s back for around 48 hours to check for a reaction. Contact eczema, which is provoked by an external substance, such as nickel allergy, comes into this category.