WOODINVILLE, WASH. – Identifying the culprit in allergic contact dermatitis often requires careful sleuthing and tailored patch testing, according to Dr. James G. Marks Jr.
Dr. Marks reviewed the current options for patch testing trays, described several cases of allergic contact dermatitis, and shared pointers for diagnosis and management at the annual Coastal Dermatology Symposium.
Dr. James G. Marks, Jr.
Allergen-screening series
Dermatologists can now choose from a variety of standard screening trays for patch testing, said Dr. Marks, professor and chair of the department of dermatology, Pennsylvania State University, Hershey. The TRUE test (the only one approved by the Food and Drug Administration) contains 35 antigens.
However, dermatologists can supplement and customize these screening trays to create a system specific to their practice and geographic area. Dr. Marks said he uses a customized tray with 100 antigens.
"The important point is there is no universal standard screening tray, so pick what works for you," he said.
"Those of you who use the TRUE test, great; as you know in the last year you have had another panel [added], so you get more screening antigens," he said. "It makes sense intuitively, and it’s proven by publications of the North American [Contact Dermatitis] Group and others that the more antigens you test with, the more positives you get and the more relevant reactions you can get," he explained.
"Then create your own," Dr. Marks advised. "So if you use the TRUE test, maybe supplement ... with a few more allergens."
Alpha-methylene-gamma-butyrolactone
Florists may come in contact with alpha-methylene-gamma-butyrolactone through handling Alstroemeria (also known as Peruvian lily), a flower popular because of its long-lasting blooms.
The compound is found in the sap that leaks out from cut stems; thus, the presentation is typically finger dermatitis, Dr. Marks said at the meeting, which was presented by the Caribbean Dermatology Symposium.
"It is the most common cause of allergic contact dermatitis in florists. So if you see florists, this is the allergen until proven otherwise," he said.
The compound is also found in the white epidermis of tulips, in which case it is known as tuliposide A. About half of tulip bulb sorters are allergic to it.
"You either patch test with parts of the Alstroemeria plant or get the allergen alpha-methylene-gamma-butyrolactone" commercially, Dr. Marks said. "I test everyone to alpha-methylene-gamma-butyrolactone, even though it’s a small subset. That’s one of my 100 [antigens]."
Methylisothiazolinone
"Methylisothiazolinone has become a very important and hot allergen," Dr. Marks commented. This allergen is increasingly used in personal care products and requires a special approach to patch testing. It is found in many wet wipes, use of which can produce, for example, perioral dermatitis.
The standard combination test antigen, applied at 100 parts per million, contains 3 parts methylchloroisothiazolinone (MCI) and 1 part methylisothiazolinone (MI), he noted. Thus, "you are really only patch testing to 25 parts per million of MI."
"The recommended concentration of patch test to MI is a bit in flux," said Dr. Marks; the North American group currently uses 2,000 parts per million but is considering halving that number, he noted.
"You can see how you can miss patients who are allergic to MI if you only patch test to MCI/MI," he commented. "So those of you who are using the TRUE test, you are going to miss patients who are allergic to MI."
"The important point is you’ve got to test both – MCI/MI and MI alone. ... You should supplement what you are patch testing with MI, certainly at least at 1,000 parts per million, if not at 2,000," Dr. Marks advised.
"The Cosmetic Ingredient Review, which sets limits for [MI] in the U.S., is going to be reevaluating, and I’m sure will be having lower limits in leave-on and rinse-off products," he noted.
Rubber accelerators
Surgeons may develop particularly problematic allergic contact dermatitis as a reaction to the rubber accelerators used in the manufacturing of many surgical gloves, Dr. Marks noted.
He described the case of a surgeon who developed severe hand dermatitis and eventually a generalized dermatitis. "In this case, if you used the TRUE test, you would make the diagnosis; he was positive to thiuram and carba mix."
Allergen avoidance entailed finding an alternative, rubber-free surgical glove, the Derma Prene Ultra glove (manufactured by Ansell), which is made of neoprene. Also, the surgeon switched to vinyl exam gloves for outpatient care.
"There may be other surgical gloves ...," Dr. Marks acknowledged. "But be sure and keep this some place because some time in the future when you have your surgeon friend with hand dermatitis, you can recommend that glove after you patch test them and prove that they are rubber-accelerator positive."