Antihistamines are the common remedy to combat the release of histamine in the body, which is the cause of many allergy symptoms such as itching eyes and runny, watery nose. Allergies affect about 50 million American children, most of whom are treated with some form of antihistamine.
Without intervention using antihistamines, the termination of the histamine effects is dependent upon the activity of specific enzymes in the body that degrade histamine. The activity of these enzymes is now known to be under genetic control which may, in part, explain differences in severity of allergy symptoms between individuals.
To gain a better understanding of how genetics affects histamine breakdown, Bridgette Jones, MD, Allergy/Asthma/Immunology specialist and Assitant Professor of Pediatrics, University of Missouri-Kansas City School of Medicine, is investigating a new technique to assess histamine response in the skin called histamine iontophoresis with laser Doppler flowimetry. Her study is funded by a Katharine Berry Richardson (KBR) grant.
"We are performing this technique on a group of patients to discern if skin blood flow response to histamine iontophoresis as assessed via the laser Doppler technique could be a surrogate marker for altered histamine metabolism in relation to histamine pharmacogenetics," says Dr. Jones. "It would be great if we could develop a screening tool that we could use clinically to look at patients and see who would benefit from antihistamines or more aggressive allergy therapies such as immunotherapy."
Histamine iontophoresis with laser Doppler flowimetry uses a low electrical current to painlessly drive histamine into the skin and into the small blood vessels of the outer skin layer. A low-energy laser positioned over the skin can directly measure the response to the histamine as indicated by blood flow to the site. This technique delivers a fixed dose of histamine which can be measured in a dynamic and continuous fashion.
"A more standardized technique would be helpful clinically and allow us to better evaluate antihistamines in the future," says Dr. Jones.
As an asthma/allergy specialist, Bridgette Jones, MD, was intrigued by patients who received standard therapy, but for some reason, didn't get better, no matter what medication they received.
"Sometimes we would assume these patients were not taking their medications, but now we know that because of their genes, they may be unable to benefit from the medication like other patients," says Dr. Jones.
It was the impact of genetics on asthma and allergies that got Dr. Jones interested in pursuing a fellowship in clinical pharmacology.
"The study of pharmacogenetics will allow the opportunity to provide therapies for patients that would benefit them the most," says Dr. Jones. "Right now we put a patient on medicine for a period and then have them come back to see if it works. Applying pharmacogenetics, we might obtain a blood sample and determine which medication they would benefit most from and get them on the right therapy right away."