NEW ORLEANS Increases in nickel allergy have done nothing to make the diagnosis of contact dermatitis a more exact science, according to a pediatric dermatologist.
In her update on contact dermatitis, Dr. Lisa Garner, a private practitioner from Garland, Tex., also discussed the diagnosis of fragrance, local anesthetic, and plant allergies.
Nickel recently received special recognition from the American Contact Dermatitis Society ("Nickel Named Contact Allergen of the Year," SKIN & ALLERGY NEWS, February 2008, p. 1).
It is the most frequent positive patch test allergen worldwide, and in the United States only poison ivy/oak is responsible for more allergic contact dermatitis (ACD). Nickel allergy now stands at almost 19% of all persons who are patch tested in referral centers, though the definite relevance is far less, Dr. Garner said at a dermatology update sponsored by Tulane University.
Body piercing appears to be the primary risk factor for ACD today, while nickel in earrings, snaps, and belt buckles remains problematic. In one study, investigators found that 16% of blue jeans tested positive for nickel (Dermatitis 2007;18:20811). Coating these products with a nail hardener or a nickel guard can prevent the release of nickel.
There are now reports of reactions to orthopedic devices, orthodontic appliances, and, more recently, stents, with anecdotal reports of restenosis occurring more frequently in nickel-allergic patients. "But if you see dermatitis over a knee implant, this is more likely to be a reaction to an analgesic rub, tea tree oil, or other substance. First look for these as a cause of the local reaction," she advised.
Nickel-allergic patients can assess the nickel content of household and personal objects using the Delasco or Allertest Ni (Allerderm) kits.
Fragrance was the American Contact Dermatitis Society's allergen of the year in 2007 (Dermatitis 2007;18:37) and is the fourth most common patch test, though definite relevance is hard to document for an individual patient, Dr. Garner said.
Fragrances are practically ubiquitous in products, and individual compounds are not listed on product labels. "Having an allergic reaction to one fragrance does not mean a patient will develop ACD to all fragrances, and there is no way to find out which fragrance a patient is actually allergic to," she said. "Patients with a strong reaction to patch testing will have to be cautious with the introduction of any new product. The stronger their reaction, the more likely they are to be strongly allergic to another fragrance."
To improve the ability to detect fragrance allergy, six European centers developed the fragrance mix II patch test in 2005. This test contains citronellol, lyral, hexyl cinnamal, citral, coumarin, and farnesol.
Still rare, though becoming more common, is ACD to local anesthetics, since these compounds are being increasingly included in prescription and over-the-counter products. Allergic reactions include localized or generalized eruptions as well as delayed-type hypersensitivity reactions, said Dr. Garner, who had no conflicts to disclose.
In 2007, investigators reported 16 cases of positive patch test reactions to lidocaine out of 1,143 patients tested over 5 years (Dermatitis 2007;18:21520). Two had lidocaine as their only positive test, and three of eight who underwent intradermal testing had positive reactions.
Certain natural compounds are responsible for an increasing number of positive patch tests. Toxicodendron, Compositae, and tea tree oil are the most common botanic allergens; they contain sesquiterpene lactones, over 100 of which have been identified, she said.
Patients can be tested using the sesquiterpene lactone mix (alantolactone, dehydrocostus lactone, and costunolide), which is specific but lacks sensitivity, and the compositae mix (short ether extracts of arnica, Germany chamomile, yarrow, tansy, and feverfew flower extra), which is more sensitive. Tea tree oil elicits positive patch testing in 0.5% of individuals, so it has been added to the North American Contact Dermatitis Group standard tray.
"Be sure to patch test the patient to their own products," Dr. Garner added.
Dr. Garner also noted that new thin-layer rapid-use epicutaneous test allergens were released this year, including imidazolidinyl urea, diazolidinyl urea, tixocortol-21-pivalate, and budesonide. Patch testing to tixocortol and budesonide identifies 91% of steroid-allergic patients (including D2 steroid patients) but does not identify patients allergic to betamethasone valerate or clobetasol propionate (D1 steroids). Quinolone mix has also been added, which should identify allergen sources in paste bandages, topical antibiotics and antifungal creams, lotions and ointments, and animal food.