About allergy and eczema
Allergic disorders are on the increase in the UK and across the world, affecting up to 40% of the population. Allergic disorders include food allergy, eczema, asthma and allergic rhinitis (commonly known as ‘hay fever’). They also include reactions to specific allergens such as medicines and insect stings.
What is an allergy?
An allergic reaction is an immune response to a substance to which the person has become sensitised. A substance that causes an allergic reaction is known as an allergen (e.g. pollen, animal dander, dust, certain foods and chemicals). Many allergens are harmless in themselves but in sensitised individuals cause the body to overreact. Allergies can be broadly divided into two groups: immediate and delayed allergies.
Who gets allergies?
We are unsure why some people develop allergies and others don’t. We are aware of factors which make it more likely that a child will develop some form of allergic disease, such as family history. Children who are born into a family where their parents or siblings have some form of allergic disease are more likely to develop allergic disease themselves. However, as a parent you do not pass on the specific allergy (i.e. if you are peanut allergic, this does not mean your child will be peanut allergic), rather you pass on the predisposition for your child to develop allergic disease of some sort, be that eczema as a young baby or hay fever in adulthood.
People who are predisposed to develop allergic disease are known as atopic individuals. We know that babies with eczema in the first few months of life have an increased risk of developing food allergy.
The skin is a protective barrier and keeps bacteria, viruses and allergens out of the body. Those with eczema have a disturbance in this barrier, and we now believe that this disturbance is a route which allows allergens to enter and sensitise the body.
What are the criteria for getting a referral for allergy testing?
The criteria for allergy testing is based on the patient’s best interests. There are three types of allergy testing for foods: IgE blood tests, prick tests and challenge tests. No one test is 100% reliable and usually a combination of tests is undertaken. The interpretation of these tests requires an expert in allergies or dermatology to review the results, as it is often not a clear-cut process.
Allergy testing referral on the NHS is considered appropriate for people with symptoms of an immediate allergy, that is, an allergy occurring within a few seconds of eating a food and up to two hours after eating the food. Symptoms include vomiting, lip swelling, tongue and throat swelling, hives and difficulty breathing.
Allergy testing is also appropriate for people with moderate to severe eczema which cannot be controlled with topical treatments. If your eczema is moderate to severe, it is likely that you will be under the care of a dermatologist, with whom you can discuss the merits of allergy testing further.
Although environmental allergens, such as pollen and grasses, can be tested for, testing is not routinely carried out, as the knowledge that you are allergic to them does not change the outcome. The expectation is that all patients with eczema should take steps to minimise environmental allergens where they can, for example, by closing windows when pollen counts are high. With time, patients will come to know what makes their eczema worse, and can avoid the relevant allergens without needing the allergy confirmed with a test result.
Private allergy testing can be arranged directly if you are self-funding. If you are arranging the testing through a private medical insurance provider, a doctor’s referral is still required.
For more information on allergy and eczema, please see our Allergy factsheet