SKIN TESTING and IMMUNOTHERAPY

Please see my initial sections in Allergic Diseases prior to reading this section so that you understand the basic allergic mechanisms.

Skin testing appears relatively simple to do. The problem is doing it accurately so that you obtain reliable and repeatable results. The variety of skin testing techniques available, whether it be scratches, pricks, or needles (intradermal) all assess type 1, immediate, IgE mediated allergy. This is important to remember, as there are other types of allergy as outlined in the Allergic Diseases section.

Skin testing can be done on virtually every individual. There are no other testing methods that are as accurate as skin testing (and their are testing " methods " performed that are totally unreliable). Only those persons with severe generalized skin problems present difficulties in skin testing. Testing should be done in any individual suspected of having allergies or asthma. Testing is done to confirm suspected allergy and give additional information to that obtained from a history and physical exam. Testing can be done at any age and is extremely important in very young infants to guide avoidance measures and give these children a better chance of not developing future allergic problems (true prevention). The minimum battery of skin tests (infants) is approximately 12, and the maximum usually 40 to 50.

I prefer the scratch technique, on the forearm if possible, so the patient can see the procedure being performed (this lessens anxiety), and particularly, so they can observe the results. In certain circumstances, further testing will be done by the intradermal method when we want to absolutely prove no evidence of allergy. The intradermal method gives more false positive results, can result in more severe allergic reactions, but is very useful to rule out a specific allergy. The testing itself must be done very consistently by the same individual. Interpretation, similarly, must be done by the same individuals, and requires a tremendous amount of experience for reliable and consistent interpretation.

Further discussion of interpretation is well beyond this talk. What I want to address are some of the many pitfalls that occur with skin testing so that an individual has some idea whether they have been properly tested. In my opinion, the worst case scenario for skin testing, is when an individual has poor testing done and is told they have no allergies. These individuals never again question this and often spend the rest of their life suffering from a condition that is highly amenable to treatment. The skin testing should be chosen to specifically address that individual's allergy symptoms. Blanket standard testing indicates a lack of taking the individual patient's specific problems into account. Many medications block skin testing. Medications such as ASA, ibuprofen, NSAIs (arthritis, pain, anti-inflammatory pills), many antidepressants, all cold-cough-decongestants-antihistamine preparations, many blood pressure or heart medicines, many herbals, other medications and even acetaminophen in certain circumstances can block skin testing results. Ideally, the person being tested should avoid all medicines-herbals for 3 days prior to testing. A positive histamine control must be used during the skin testing, only this gives the allergist the ability to determine what a significant positive skin test will look like, and if positive, ensures that the patient can be skin tested at that particular time (i.e. the patient does not have medication in them that will block testing). When the skin testing is performed, there should be no cross contamination between each individual test. I routinely have the tests interpreted at 5 and 20 minutes, and often again at 30 minutes or more. Skin testing should always be interpreted up to at least 20 minutes after the test has been performed. The skin testing results must be interpreted in conjunction with the individual's history as to whether the positive test represents true clinical allergy. In general, skin testing for inhaled allergens is approximately 80% accurate, but for foods is much lower than this. This is why it is critical to interpret skin testing within the context of the individual's specific problem. Again, negative skin testing is highly accurate to rule out type 1 IgE allergy. Some individuals have dermatographism, a condition where scratching or pressure on the skin causes a wheal (hive or bump). When these individuals are skin tested, you often have to wait between one and two hours to read their skin test results. These patients often state that they were skin tested before and " were allergic to everything " (which is impossible). Taking an oral antihistamine after skin testing will limit swelling and itching, particularly if the person has major positive skin tests. The material for skin testing must be appropriate. We have available standardized test material for very few allergens. Using fresh testing material can be more accurate than commercial preparations in certain circumstances, particularly when dealing with certain foods.

The bottom line is that your skin testing must be done properly, with appropriate testing material, interpreted by individuals with tremendous experience in this area, and must always be interpreted in relation to the specific problems that each individual has. Skin testing is often not done well, and if there are questions about the accuracy of previous testing, retesting is indicated.

IMMUNOTHERAPY (ALLERGY SHOTS)

There are a variety of types of " immunotherapy ". In this section I specifically am discussing the most common type of immunotherapy-"allergy shots"-"allergy serum", that involves giving an allergic individual needles into the subcutaneous tissue (the loose tissue directly underneath the skin). These injections are given frequently at first (often weekly), with each injection increasing the amount of specific allergen given, until an adequate dose is attained. Once this full dose has been reached, the injections are usually given approximately once per month. There are other time schedules used for specific circumstances and patients. Please see my information sheet regarding immunotherapy. This discussion centers around specific factors you should be aware of regarding allergy shots.

Immunotherapy can only be done for specific allergens (substances you are allergic to). These allergens must be able to be purified and quantified so they can be used for skin testing. If you are allergic to a specific allergen, and you have a clear cut positive skin test to this allergen, consideration can be given to immunotherapy. Generally, only three or four specific allergens should be put in an allergy serum. The more allergens you put in a serum, the more dilute the serum is, and the more likely it will NOT produce significant desensitization. Multiple mixtures are useless (i.e. a serum containing mixed trees, mixed weeds, mixed grass, mixed molds, etc.). Single mixtures can be useful (i.e. mixed grasses alone, mixed trees alone), but better than this, is specific immunotherapy made up tailored to your specific allergies (i.e. birch, ragweed). Molds should not be mixed with other allergens if at all possible as molds tend to destroy the other allergens in the serum. There are different preparations available to be used pre seasonally or long term and fast release (aqueous) or slow release (adsorbed). Generally the longer you are on an allergy serum and the higher the dose tolerated, the better the resulting desensitization. For many individuals after three to five years of immunotherapy, they have achieved lasting desensitization, and they can stop their immunotherapy, with continuing long term benefit. However, there are clearly a group of individuals who require their immunotherapy continuously long term to maintain benefit. In my experience, this also depends upon the specific allergen. For example : immunotherapy to hymenoptera venom, most individuals can stop at 5 years; immunotherapy for mold, most individuals require long term treatment. Immunotherapy is more effective and safer when administered by allergists or physicians with experience in this area. I very commonly see errors made in immunotherapy administration by the inexperienced. Allergy shots carry a very low risk when given by individuals with experience. However, every year a person will die from allergy shots, invariably caused by improper administration. One of the truly unique things about immunotherapy, is that the most severely allergic individuals (anaphylactic, severe asthmatic, etc.) are the very individuals who obtain the most benefit from immunotherapy. It is also clear that immunotherapy for allergic rhinitis can prevent the development of asthma in certain individuals. We know that immunotherapy for inhaled allergens is very effective for individuals with allergic rhinitis and/or allergic asthma. However, it must be kept in mind that immunotherapy does not replace appropriate avoidance measures (i.e. removing the cat, the dust / mold free bedroom) or the use of appropriate medication - although, it often significantly reduces the amount of medication required. Although immunotherapy can be done for foods (I have desensitized several patients to different foods), this is not standard practice, and has been associated with reports of deaths (peanut desensitization). Immunotherapy for food anaphylaxis is awaiting the development of safer immune vaccines. If you are taking immunotherapy, you should be aware of an important concept. I often describe allergy as being much like a pyramid. The base of the pyramid is made up of all your basic allergy exposures. The top of the pyramid is made up of acute allergy exposures (for example : during a pollen season you are allergic to, eating a food you are allergic to, etc.). If you reach the top of the pyramid, you develop increasing allergy symptoms. When you receive immunotherapy, you are being deliberately given a substance you are allergic to. You must make sure that you are not near the top of the pyramid before getting your allergy shots, or you may reach the top of the pyramid ( have a reaction to your allergy shots). So, if your allergies or asthma is flaring, you do not get your allergy shots. Also, most serious reactions to allergy shots occur within 30 minutes of administration. The bottom line is : you must wait 30 minutes in your physicians office after every allergy shot.

In summary, there are specific allergy patients who benefit tremendously from immunotherapy with a significant reduction in symptoms and medication use. Immunotherapy carries with it certain risks. However, proper immunotherapy requires an unbroken chain of appropriate events : proper patient, proper physician, proper testing, proper interpretation, proper immunotherapy materials, proper immunotherapy schedule. Immunotherapy is highly successful when all these conditions are met and there is clear and complete understanding of the process by both patient and physician.