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SAN DIEGO – Approximately one-quarter of patients diagnosed with physical urticaria actually responded when challenged, based on data from a study conducted at the National Institutes of Health.
Before patients change their lives and start taking antihistamines for a physical urticaria, they need to be challenge tested to make sure they actually have one, the researchers noted.
Dr. Hirsh Komarow
"Some of these patients were taking a lot of medication for no reason," generally antihistamines, but, at least in one patient who tested negative, cyclosporine and methotrexate, said lead investigator Dr. Hirsh Komarow, a staff clinician at the NIH’s National Institute of Allergy and Infectious Diseases.
Among 73 patients diagnosed with a physical urticaria and referred to NIH by their allergist or dermatologist, 19 (26%) did not develop hives from their presumed trigger or any others after exhaustive challenge testing. The patients had been off antihistamines for at least a week to ensure that their reactions weren’t blunted.
Nine patients (12%) did not react to their presumed trigger but reacted to others, and 45 (62%) reacted to their presumed trigger.
The rate of negative challenges was low in cold-induced (8/32, 25%) and delayed-pressure urticaria and dermatographism (2/7, 29% in both cases), but high in cholinergic (14/21, 67%) and solar (2/3, 67%) urticaria. Negative challenges were more than twice as likely in women as in men. All of the five negative patients rechallenged a year later remained negative.
Because of the time and resources involved with challenge testing, "allergists often rely on a patient history for diagnosis and selection of intervention strategies," but the physical urticarias "should be verified ... particularly when severe" enough to require life-style changes and medication, the researchers noted. "Physicians that are unable to perform testing ... may consider referral to a tertiary center for evaluation."
Overall, patients reported symptoms for an average of 9 years. Patients who tested negative reported symptoms for a mean of 6 years. It’s possible that these patients had a physical urticaria at one point, but, "Maybe it went away. Most of these go away in 5 years," Dr. Komarow said at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.
In general, physical urticaria patients change their lives to avoid triggers. "There are a million things they do. People who react to cold, for instance, won’t go skiing, they won’t go swimming, and they won’t go to the football game with their kids. They won’t go to the frozen foods section of the supermarket," Dr. Komarow said. Cholinergic urticaria patients "won’t exercise. They won’t go in the sauna; they won’t go in the hot tub. Once they find out they don’t have physical urticaria or that it’s very mild, they say ‘I feel free,’" he said.
The subjects had been referred to NIH for participation in a large, ongoing physical urticaria trial headed by Dr. Komarow.
Their median age was 31 years, and 48 (66 %) were women. The 19 challenge-negative patients were slightly younger, with a mean age of 28 years. The majority of subjects overall, and those who were challenge-negative, rated their symptoms as moderate to severe. About half the subjects in the study had atopic tendencies, detected by serum IgE and other measures.
Among other techniques, cold urticaria was challenged with beakers full of ice water, cholinergic urticaria with treadmill exercise, and solar urticaria with sun lamps. Patients were then observed over 24 hours.
The work was funded by NIH. Dr. Komarow has no relevant disclosures.