SAN ANTONIO — Treatment of chronic urticaria can be challenging, but recent findings on the condition may help improve outcomes, Dr. Aniko Kobza Black reported at the annual meeting of the American Academy of Dermatology.
One new advance is the usefulness of the autologous serum skin test (ASST) in screening for autoimmune urticaria, even though positivity can persist after clearing in autoimmune urticaria. With other types of urticaria, the test becomes negative as the condition improves and resolves.
Another recent finding is the association between a positive ASST and multiple drug sensitivities in patients with acute urticaria, said Dr. Black of St. John's Institute of Dermatology, St. Thomas Hospital, London.
Yet another new finding related to the ASST “may have practical implications.” Dr. Black explained that by using plasma rather than serum in the test, the positive test rate can be increased from 55% to 86% in patients with chronic urticaria. “There is an additional factor in plasma that induces histamine release, and it's now been shown that in chronic urticaria, there is increased thrombin formation. Thrombin can activate mast cells, so the modulation of the coagulation system with anticoagulants may prove useful in therapy for urticaria.”
The role of Helicobacter pylori in chronic urticaria is controversial. About 40% of patients have abdominal symptoms, but no evidence shows H. pylori infection causes the condition. It may be that it plays an indirect role in genetically predisposed individuals, but this remains unclear.
First-line treatment for chronic urticaria remains low-sedation antihistamines. The use of doses above recommended levels remains controversial—it seems to be clinically effective in some patients, but no trials have shown efficacy with the approach.
In rare cases, antihistamines may actually aggravate urticaria. Allergic reactions can occur in minutes but usually occur after 6 hours, and they have been seen with each type of antihistamine. No definite cause is known, but the reactions may be the result of a direct effect on mast cells.
When deciding on treatment, first consider possible side effects, then ease of administration, and then cost, she advised.
It is not possible to predict which treatments will be effective in a given patient. When first-line antihistamine treatments and combinations aren't adequate, it is important to reassess disease severity, patient history, and ASST status before trying the second- and third-line treatments because of the risk of side effects. All three types of treatments can be combined, however, “and indeed they usually have to be,” Dr. Black said.