Harold Kaiser (Practicing Allergist and Clinical Professor of Medicine, University of Minnesota Medical School) gives expert video advice on: When should I see a doctor if I think I have allergies?; Are allergies genetic?; What are the tests to find out if I have allergies? and more...
What are the symptoms of allergies?
The symptoms of allergies depend on what the allergic problem is. For example, for allergic rhinitis or hay fever, symptoms are nasal congestion, sneezing, a stuffy or runny nose, itchy eyes and the like. The symptoms of allergic asthma are coughing, wheezing, and shortness of breath. The symptoms of an allergic skin reaction may be hives or an itchy red skin. The symptoms of a food allergy may include those of the respiratory symptom and also the skin reactions such as hives or itching, and on occasion they include gastrointistinal reactions such as nausea, diarrhoea, and vomiting. These are less common than the skin reactions or the upper respiratory congestion in allergic reactions to foods.
When should I see a doctor if I think I have allergies?
If it's a nuisance you may want to go to the pharmacist and try an over-the-counter antihistamine. If it's more than a nuisance, there are good medications and good advice available from your physician that can help you significantly. So after it becomes more than a little thing, see a doctor.
Are allergies genetic?
Allergies are genetic but they are not strictly genetic the way that blue eyes or red hair may be genetic. They run in families and there are genetic markers that are common in the offspring of patients who have allergies, in other words they run through the families, but it's not directly and it's not only genetic. If you have a history of allergy in your family, that's probably the best indication that you are potentially at risk to have allergies in your own life.
What are the tests to find out if I have allergies?
The tests for allergies include first of all, a careful, thorough, unhurried history and physical examination by a qualified person. Somebody who is trained and who is sympathetic and who will understand what you are talking about. Beyond that, there are certain tests that may help us. There are allergy skin tests which help to identify the allergens if you will - the causes of the potential allergies. There are blood tests which may do the same thing. There are pulmonary function or breathing tests which may help identify if you have asthma or an allergic reaction in the lungs.
What is a "challenge test"?
If the diagnosis is murky, one of the things to consider is a challenge test. In other words, the patient is given a sample either by inhalation, or by ingestion, or by injection, of something that he or she may or may not be allergic to, and one then sees what happens. One is observed and their breathing is measured. It's something that is not routinely done. It should be done by someone who is experienced in it and generally challenge tests are done in an emergency room set up or a medical facility where you can treat the reaction if something goes wrong. The challenge test is not a routine test.
What is a "scratch test" and an "intradermal test"?
Intradermal means in the skin and allergy skin tests are typically either scratch tests or intradermal. A scratch test means, as the name implies, a scratch is made on the skin and potential allergens, again think of grass pollen or dust or cat dander, is applied to the scratch. In about fifteen to twenty minutes, if the patient is having an allergic reaction, you will get a redness which we call a wheel and flare reaction which indicates a positive reaction. If there is a positive reaction, then one can assume that the potential that this indicates an allergy is present is there. Now, some patients don't react to the scratch test and they need a stronger test. A stronger test means the same substance is injected with a needle intra the skin, or intradermally, and for some patients it's necessary to get to that stronger test to get an answer.
What is a "skin prick test"?
A skin-prick test and a scratch test are essentially the same thing. The technique may be a little bit different; some people will use a little needle and prick the skin, others may use a little device and scratch the skin, but they're the more sensitive test. If a skin-prick test is not reactive, then an intradermal or injection in the skin is the next stage.
What is a "radioallergosorbant test" or "RAST"?
The radioallergosorbant test or RAST test as it's more commonly known is a blood test which shows the presence or absence of antigen-specific immunoglobulins. What that really means is it's a blood test which indicates -- as a skin test indicates -- the presence or absence of allergic antibodies in the patient. The blood test is sometimes used in those patients for whom a skin test is not appropriate. These conditions might include: eczema of the skin; fear of being scratched up; a patient who's taking antihistamines which may inhibit the reaction; or some patients are just more comfortable having a blood test drawn than having their skin scratched. The advantage of it is it's a blood draw and the blood is sent off to the lab and one gets a quantitative answer. The disadvantage of it is it takes a longer time. A scratch test or an intradermal test takes 15 to 20 minutes. A RAST test takes overnight or a few days, depending. It's more expensive, typically, and in experienced hands, the scratch test and the intradermal test are more sensitive than the RAST test.