Is there a literature or community standard of practice basis for establishing a "maximum number" of allergens to include in multiallergen SCIT?

A common scenario is a polysensitized patient [often they are skin test positive to "nearly everything"] and end up with a SCIT prescription which can include up to 30-40+ allergens (facilitated by the use of mixes) in order to "include everything that is positive" but try to eliminate cross-reacting allergens whenever possible. Comparing our prescriptions with those around us and around the country, we have noticed that

1) Some circumvent this by testing less than 40 [ie a neighboring clinic skin tests to 20 airborne]. It is unclear how the allergists of that group arrived to a consensus of what to test for

2) A local academic medical center circumvented this by choosing the largest skin test results in creating a "pauci-allergen" prescription. A person had 16 positive skin test results and 6 allergens were included in SCIT (those that were > 6-8mm with particular attention to include "classic allergens" like ragweed and birch were included)

3) The few that do include nearly as many allergens as we do, "dose lower" so that the top dose is typically 1/10 the strength of a typical single allergen SCIT maintenance dose (in other words, the maintenance dose stops at vial 1:10)

We are trying to adjust our immunotherapy to be more consistent with guidelines.

A potential solution to the equation would be to limit the number of allergens. Do you have any guidance on how to "limit allergens" or even if this is necessary, at least until allergen components are available for diagnostics and therapy?

An example of a "not too uncommon prescription":

9 grasses [brome oat velvet bermuda KYblue rye orchard redtop sweet vernal]

16 trees acacia ash birch elm maple/elder oak olive cottonwood alder walnut sycamore cypress/juniper liquid-ambar mulberry eucalyptus pine

14 weeds Baccaris Careless weed Cocklebur Firebush/Koch Lambs Q Pigweed E. Plaintain
R. Thistle Dock/Sorrel ragweedmix sage scale alfalfa

2 animals cat APdog

1 mite

(1-3 molds)


Thank you for your inquiry.

I am forwarding your question to Dr. Hal Nelson who is an internationally recognized expert in immunotherapy and allergen crossreactivity in this regard. When we receive Dr. Nelson’s comments, we will forward them to you.

Thank you again for your inquiry.

Phil Lieberman, M.D.

We received a response from Dr. Nelson. Thank you again for your inquiry and we hope this response is helpful to you.

Phil Lieberman, M.D.

Response from Dr. Hal Nelson:
There was no information regarding the location of your practice. However, there are certain general observations: 1) a positive skin test is not, per se, an indication for inclusion in the extract. There probably is a relationship between size of prick skin test and likelihood of symptoms on exposure. 2) Many pollens to which a patient may react are from primarily insect pollinated plants or plants that do not grow in profusion so that they contribute very little pollen to the overall pollen load and therefore do not require inclusion in the treatment extract even if the patient is prick skin test positive. 3) There is, as you note, considerable cross-allergenicity that can be used to decrease the number of allergens employed.

In regard to your example of "a not too uncommon prescription" I offer the following comments:
9 grasses [brome oat velvet bermuda KYblue rye orchard redtop sweet vernal]
Comment: This is a good example of cross-allergenicity. All of the pollen extracts except Bermuda are in the highly cross-reactive group of Pooideae and can be covered by timothy alone, or mixture of 3-4 of the ones most commonly encountered in your area. If a mixture is used, the total amount should be the same as for a single pollen extract.
16 trees acacia ash birch elm maple/elder oak olive cottonwood alder walnut sycamore cypress juniper liquid-ambar mulberry eucalyptus pine
Comment: Are all these trees important pollen sources in your area? Some are usually found in cold climates (Birch) while eucalyptus, mulberry and olive are usually found in warmer climates. Pine is rarely a cause of allergic symptoms.
14 weeds Baccaris Careless weed Cocklebur Firebush/Koch Lambs Q Pigweed E. Plaintain

R. Thistle Dock/Sorrel ragweed mix sage scale alfalfa
Comment: The weeds can usually be covered with a single predominant member of each family (Chenopod/Amaranth, Heliantheae (ragweed, cocklebur), Artemisia, or with a small mixture if more than one major pollen contributor is present in the area. Again, if a mixture is used, the amount of each pollen extract should be reduced. Alfalfa probably is largely insect pollinated.
2 animals cat AP dog and 1 mite
Comment: If these are indicated and used in appropriate amounts, they will require one vial. If all are not indicated, you may be able to add a couple of pollen extracts here and avoid 4 vials.
(1-3 molds)
Comment: Mold extracts are generally of very poor quality and except for Alternaria and Cladosporium, there is limited evidence for the clinical importance of any one mold. Never the less, if you feel treatment of mold allergy is indicated, these extracts should be kept separated from all the others and hence this dictates another vial.
Hal Nelson
National Jewish Health

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