Allergy medications may indeed make a subsequent allergic attack even stronger, according to a study.
Pal Johansen at the University of Zurich, Switzerland, conducted a study on mice to determine the long-term effects of antihistamines medicines known to offer a great way to fight off an allergic attack on the immune system.
He and his colleagues injected 50 mice with bee venom, a substance to which almost all organisms develop an allergy upon exposure. Half of the mice were also given 100 micrograms of the antihistamine Clemastine just before they were given venom, and 100 micrograms on each of the two days afterwards.
After six weeks, the researchers injected the mice with another dosage of bee venom, and monitored the allergic reactions. They found that mice given antihistamines reacted more violently to the second venom injection.
"We believe that the antihistamines were doing more than disrupting the immediate immune reaction to the first venom dosage. We think they were also keeping the immune system from getting used to that dosage," Nature magazine quoted Johansen as saying.
The findings, published in Clinical and Experimental Allergy, suggest that the mice on allergy medication had not developed tolerance to the allergen.
In the second part of their research, the researchers desensitised the mice to the bee venom by using immunotherapy, a process of introducing tiny amounts of an allergenic substance to an allergic individual, slowly helping the immune system to tolerate the substance.
They found that mice that had originally been administered the allergy medication responded more poorly to the immunotherpay than the other mice, when sensitised with venom.
"This was really surprising because others, have claimed that antihistamines would aid the process of immunotherapy, and that is simply not what we saw," says Johansen.
However, Cezmi Akdis, director of the Swiss Institute of Allergy and Asthma Research in Davos, feels that more research is required on the subject because there is no evidence that rodents and people metabolise Clemastine at different rates.
He points out that only two studies have so far suggested that antihistamines help immunotherapy, and that the current study is the first to contradict them.
"We definitely need more research in this area," he says.