Best Way to Diagnose an Allergic Disease

The diagnosis of an allergic disease has to be based on a careful medical history taken by a doctor and you may have to be referred to a specialist. All your symptoms need to be described in detail before a doctor can determine whether or not you have an allergic disease and decide on a course of management.

The nature of any conditions that make the symptoms worse, or trigger factors, and the frequency and dur­ation of your symptoms, are all important considerations. Not all problems, even though they may be similar to those produced by allergens, are, in fact, allergic in nature.

A tendency to house-dust mite allergy, one of the most common of all allergies, is suggested by several “yes” responses to questions such as, for young children:

• Does your baby sneeze when you lay him or her on the bed in the morning?
• Is your child often troubled with conjunctivitis and eczema?
• Did your toddler get a “cold” and cough when moved to the “big” bed, and has continued snuffling ever since?
• Do your children appear to contract a “cold” when they stay with relatives or friends?
• Have you had a positive skin test to mites?

And, for adults and older children:

• Do you sneeze, get itchy hands or face, or become breathless when making the bed and vacuuming?
• Do you sneeze or get a tight chest in the morning or after getting into bed at night?
• Do you wake up at night with itchy eczema or a blocked or runny nose and are kept awake because of it?
• Do you get night asthma?
• Do you feel better when you are outside the home?
• Do your symptoms disappear on holiday (vacation) in a warm, dry climate, only to reappear soon after returning home?
• Do your symptoms become worse in the autumn (fall)?

The presence of an allergic tendency is suggested by a family history of allergic problems and can be tested for by checking whether or not you have an elevated immunoglobin E (IgE) response to specific allergens

Skin-prick tests

The most widely used allergy test is the skin-prick test. This is based on the fact that IgE binds to special cells in the skin, called mast cells, and that when allergens come into contact with the IgE the mast cells release chemicals that produce an itchy reddening of the skin with a central bump. The size of the bump reflects the strength of the reaction. Many tests to different allergens can be carried out at once. Results are apparent after about 15 minutes.

Blood tests

A blood sample can be analyzed for specific IgE. The laboratory will check for single allergens as well as for multiple allergens. The advantages of a blood test are that it is not influenced by drug treatment and can be given to people who have widespread skin diseases. The disadvantages, compared with skin-prick tests, are that blood tests are expensive, may not be as sensitive, and results are not instant.

Patch tests

A patch test is widely used in the diagnosis of contact allergies. Several standard series of contact allergens are available. These are placed on the skin (often on the back), strapped in place, and left for between 48 and 72 hours before the skin is inspected. These tests can be undertaken only by an expert, since it is important to distinguish an allergic response from an “irritant response”.