Dr. Joseph F. Fowler, Jr.
WAIKOLOA, Hawaii – Contact allergy to a corticosteroid molecule is considerably underdiagnosed – and it’s no wonder why.
Even when suspicion runs high enough that patch testing is performed, the anti-inflammatory action of the corticosteroid often masks the allergic contact reaction, at least early on, Dr. Joseph F. Fowler Jr. said at the annual Hawaii dermatology seminar sponsored by Skin Disease Education Foundation.
Contact allergy to the corticoid molecule itself – not to some component of the medication’s vehicle – is by no means rare. The incidence in various studies is 0.5%-5%.
“Just because it’s an anti-inflammatory molecule doesn’t mean your body can’t make an allergen to it,” observed Dr. Fowler of the University of Louisville (Ky.).
Contact allergy to a corticosteroid should be suspected when a patient has a long-standing skin disorder that isn’t responding to appropriately prescribed topical steroid therapy, or when a dermatitis is getting bigger and bigger as the patient applies more medication, he said.
Contact dermatitis experts divide corticosteroids into the following five groups for allergy purposes, based on their molecular structure:
– Group A, known as the hydrocortisone type.
– Group B, the triamcinolone acetonide type.
– Group C, the betamethasone type.
– Group D1, the betamethasone dipropionate type.
– Group D2, the hydrocortisone-17-butyrate type.
In the United States, because of usage patterns, at least 90% of cases of corticoid allergy involve Group A, and most of those involve hydrocortisone. Allergy to Group B steroids is the next most common, accounting for 5%-7% of cases. Most of the rest involve Group D. Group C steroids are almost never allergenic, according to Dr. Fowler, who is the current president of the North American Contact Dermatitis Group.
Tixocortol pivalate is the standard agent that represents Group A in patch testing. The others in Group A are fludrocortisone acetate, hydrocortisone acetate, and – importantly – methylprednisolone and prednisone. Cross-reactivity can occur within steroid groups, so a patient with contact allergy to a Group A steroid that’s used in topical medications could be at risk for a serious reaction to oral or injectable prednisone, he noted.
Group B is composed of all the steroids ending in ‘–ide.’ Budesonide is the one used as the Group B representative in patch testing. Group D steroids all end in ‘-ate.’ Clobetasol propionate is employed as the representative of Group D1 in patch testing; hydrocortisone-17-butyrate is the test material for Group D2.
Group C, which almost never causes contact allergy, is a select group that comprises clocortolone pivalate, desoximetasone, and dexamethasone. When allergy to corticosteroids is known or suspected, a switch to a Group C steroid is the safest bet. Clocortolone cream is the hypoallergenic midpotency steroid of choice, whereas desoximetasone cream or ointment is the safest mid- to high-potency option, he said.
With regard to contact allergy to the vehicles used in topical corticosteroid medications, Dr. Fowler said the big offenders are the various preservatives and propylene glycol.
“Propylene glycol in a small amount is not a big problem. If it’s under 5% or 10% it’s rarely a problem. The trouble is that when you read the label, you don’t always know how much is in a product,” he explained.
When allergy to a vehicle is suspected, the safest option is to turn to a product that utilizes an ointment or spray vehicle.
Topical steroids that are free of problem preservatives and propylene glycol include desonide ointment, hydrocortisone-17-butyrate lipid cream, clocortolone cream, triamcinolone spray, and – in the high-potency range – halcinonide ointment, amcinonide cream, fluocinonide oil, and clobetasol spray, he noted.
Dr. Fowler disclosed serving on the speakers bureaus for Coria Laboratories Inc., Galderma Laboratories LP, Medicis Pharmaceutical Corp., Novartis, Ranbaxy Pharmaceuticals Inc., Shire Pharmaceuticals, Stiefel Laboratories Inc., and UCB. SDEF and this news organization are owned by Elsevier.