Allergic reactions vary and include many different symptoms.  Some reactions can be severe and threaten life. This is called anaphylaxis. Some people have a condition called ATOPY (eczema, asthma, hayfever, urticaria, allergic rhinitis) which makes them prone to allergies.

Testing for allergies can be complicated and is not always necessary.  An allergy is a response by the body’s immune system to something (called an allergen) that is not necessarily harmful in itself. Some allergic reactions are mild and harmless, but others are severe and potentially life-threatening (anaphylaxis). A food intolerance is not the same as a food allergy. Many patients incorrectly use the words interchangeably.  A food allergy occurs when the body’s immune system reacts abnormally to specific foods.  No allergic reaction occurs with food intolerance. Patients with food intolerance may have digestive symptoms such as diarrhea, abdominal cramps and bloating. These are quite common symptoms anyway. In food intolerance the symptoms may be caused by difficulties digesting certain substances in food.  One example is lactose, a sugar found in milk and dairy products. 

Differences between food allergy and intolerance include:

The symptoms of food intolerance occur usually a few hours after eating food. Allergic reactions happen much more quickly.

With allergy, even a tiny amount of the food can cause an allergic reaction to take place. Some people with a severe allergy to nuts might experience anaphylaxis after eating something made in a factory that also handles nuts, or after kissing someone who has recently eaten nuts.  Food intolerances are never life-threatening.  Other allergies can be life-threatening. 

Allergic contact Dermatitis is a dermatological diagnosis. Patients either self-refer or are referred by their GP to the Dermatology clinic with recurrent and persistent itchy scaley rashes. The Dermatologist will then suggest patch testing to try and identify the allergen. 

There are 3 different types of allergy testing.  Your GP or Doctor can perform an IGE/RAST test where a blood sample is sent to the laboratory for testing.  This test measures the amount of IgE antibody (the Immunoglobulin protein made by the Immune system) in the blood that has been produced against a specific allergen. RAST is recorded from 0 to 6, depending on the amount of allergen-specific IgE.  A result of 6 means there is an extremely high level of IgE for this allergen, so the person is very sensitive/allergic to that allergen.  You can test for IGE to peanuts, latex, tree and grass pollen, house dust mite, eggs, animal dander, penicillin etc.

A skin prick test can also be carried out by the Doctor and test for various allergies.  Here, the allergens are mixed with liquid to make a solution. A drop of each liquid is placed on the arm and a needle is used to prick the skin, beneath the droplet of fluid.  This means that a tiny amount of the allergen can breach the skin.  The skin is observed for an allergic reaction.  This would have to be done in a centre where full resuscitation equipment was available- so a Doctor or hospital. A blood test is safer than skin prick testing in as patient who has had a previous anaphylactic reaction. 

Patch testing is a specialist procedure carried out by the dermatology doctor.  This will be used to identify skin allergies. This is called contact dermatitis – a condition in which people develop patches of eczema (dermatitis ) as a reaction to certain substances ( allergens) that the skin is in contact with.  There are two types of contact dermatitis. Irritant dermatitis which is an immediate reaction for example to a substance like bleach. Usually here, the offending agent is obvious. The other one is called a contact allergic dermatitis.  This appears 2-3 days after exposure to the allergen in the form of a itchy red scaley rash (sometimes on the eyelids, or elsewhere on the body). Substances that can cause an allergic reaction are called allergens.  They can be found at home,  work or in leisure activities.  They can sometimes be very difficult to identify which is why patch testing may be suggested. 

There are approximately 40 substances which are most frequently in contact with the skin such as natural rubber latex, preservatives, metals, perfumes, cosmetics, leather chemicals, lanolin and plants among others.    Additional substances are sometimes added to this list if is thought it might trigger your skin condition. You may also be tested with some of your own work or home products, such as personal toiletries. You will need to attend for a initial consultation. You will need to bring a full list of prescribed medication, all ointments and creams, your own products and chemicals used at work (if you think that substances at work may be making your skin condition worse please bring in the Health and Safety Data Sheets of these products).

After the initial consultation, 3 subsequent visits to the clinic will be necessary. Your doctor will give you written information about what to expect after the first consultation.