Compositae family a common culprit: botanic allergens present interesting diagnostic challenge.
"It's very important to ask about the social history of your patient if you're doing any patch testing to figure out the nature of a dermatitis," said Dr. Zug, a dermatologist at Dartmouth Hitchcock Medical Center, Lebanon, N.H.
The distribution of dermatitis can clue in a dermatologist about where to focus a patch test. On the dominant hand of people such as florists, one might see the telltale "tulip" finger, a hyperkeratotic, tender pulpitis of the distal 1-3 fingers caused by handling tulip bulbs. Alstroemeria, a popular cut flower of more than 50 species, cross-reacts to tulip bulbs and is the most common cause of plant allergy among U.S. florists.
Botanic products may cause a generalized, patchy dermatitis. A linear distribution is often a giveaway for poison ivy, oak, or sumac. The baboon syndrome of dermatitis across the perianal and perigenital areas, as well as the eyelids and upper inner thighs, is associated with eating raw cashew nuts, among other things, she said at the meeting, cosponsored by the American Contact Dermatitis Society.
Phototoxicities are common in people who are exposed to a variety of plant families that regularly are found in cultivated perennial gardens and borders, roadsides, meadows, and the grocery store. These plants include carrots, parsnip, limes, false bishop's-weed, common rue, and angelica.
Many plants from these same locales can cause allergic contact dermatitis. For example, the Compositae family of plants includes more than 10% of the world's flowering plants, including chamomile, chrysanthemum, echinacea, daisy, dandelion, ragweed, and marigold. Sesquiterpene lactones are the most common allergens from Compositae.
Compositae "is probably the most important family of plants causing contact dermatitis, both in the United States and Europe," Dr. Zug said. Florists, people who directly handle plants, and gardeners seem at biggest risk for developing this type of allergy.
Patch testing with a 6% Compositae mix in petrolatum--arnica (0.5%), German chamomile (2.5%), yarrow (1%), tansy (1%), and feverfew (1%)--is now favored in the literature over testing with a 0.1% sesquiterpene lactone mix in petrolatum (alantolactone, costunolide, and dehydrocostus lactone). The Compositae mix is probably a little irritating, and one of its reactants may have little relevance, she said.
Some experts advise testing with both mixes, Dr. Zug said.
In one study at an occupational dermatology clinic, 4.2% of 346 patients had positive reactions to the Compositae mix, whereas the sesquiterpene lactone mix induced a positive reaction in 0.7% of 1,076 patients (Am. J. Contact Dermat. 12:18-24, 2001).
The risk of dermatitis from Compositae-containing products is unknown in patients who are sensitive to Compositae. So, it is best to test with the patient's product and the extract used in the product, as well as with the Compositae mix, sesquiterpene lactone mix, or an individual allergen if available, she advised.
To test for allergic contact dermatis caused by the oil of the Melaleuca alternifolia tree (tea tree oil), Dr. Zug advised using the oxidized form of the oil, as it is three times more likely to sensitize than fresh oil. The oil is often used for massages and is used in cosmetics and detergents and to treat psoriasis and warts.
Dermatitis found on the back of the hands, forearms, and neck signals a possible airborne wood or plant allergen. Such a distribution might be found on a woodworker exposed to sawdust.
If a wood allergy is suspected, try testing with sawdust supplied by the patient at concentrations of 1% and 10% in petrolatum. Surprisingly, pine and spruce allergies are relatively uncommon. Allergies to exotic woods, such as teak and rosewood, are much more common.
The allergens of exotic woods are primarily benzoquinones and napthoquinones. Some of the substances to screen for pine and spruce allergies include colophony, oil of turpentine, and wood tars.
BY JEFF EVANS
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|Title Annotation:||Clinical Rounds|
|Publication:||Internal Medicine News|
|Date:||Apr 15, 2004|
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