Q:

12/5/2013
Local pollen counts in the fall vary depending on the source. Some report Sage, others report Mugwort and sometimes Pigweed is reported. I have been told by some that Sage and Mugwort are cross reactive species yet patients are not always positive for both when skin tested. We are practicing on the East Coast in the Boston area. Which would be more useful to test for: Sage or Mugwort? And is Pigweed predominant enough in this area that it should always be tested for as well? Some pollen counters report it and others do not.

A:

Thank you for your inquiry.

You are correct in that all three of the weeds you mentioned (Mugwort, Pigweed, and Sage) are found in the Boston area. I am afraid the difference in levels of pollen that you note from different centers simply reflects the state-of-the-art. However, it is well established that these weeds plus several others (Sheep Red Sorrel, Plantain, Nettles, Hemp, Russian Thistle, Kochia, Amaranths, Burr weed marsh elder, Rough weed marsh elder, and of course, the ragweeds are present in your area (1). There is also a complex cross-reactivity amongst these weeds (2).

With these observations in mind, I am not sure that your question can be answered definitively, but I am going to ask Dr. Richard Weber, the author of Reference 2, to respond to your inquiry. When we receive Dr. Weber's response, we will forward it to you.

Thank you again for your inquiry.

References:
1. Solomon WR and Platts-Mills AE. Allergy: Principles and Practice, 5th edition, 1998; page 367.

2. Weber RW. Guidelines for using pollen cross-reactivity in formulating allergen immunotherapy. J Allergy Clin Immunol 2008; 122:219-221.

Sincerely,
Phil Lieberman, M.D.

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

Sincerely,
Phil Lieberman, M.D.

Response from Dr. Richard Weber:
While there are almost a dozen different Artemesia species found in the western states, the predominant one in the eastern states (and western Europe) is mugwort, A. vulgaris. We looked at Artemesia cross-reactivity several years ago (Katial et al) and found them all very, very similar. So not necessary to test for more than one I think. Differences in patients' reaction on ST may be due to relative concentration of the extract or variation in testing (depth of individual ST, site, etc). I usually recommend testing with A. tridentata in the western states and mugwort in the eastern states, and likewise for extracts in immunotherapy.

Pigweed is widespread around the globe, and should be tested for. We also looked at cross-reactivity a few years back. The two major pigweeds, redroot and Palmer's amaranth, cross-react very strongly, western water hemp is a little weaker. I usually use red root pigweed.  As far as it being reported on counters, it is very difficult to tell pigweed from other chenopod-amaranths pollens, so they are usually reported as “chenopod-amaranth” not individual weeds.

Dick Weber

AAAAI - American Academy of Allergy Asthma & Immunology