Based on a review of 47 trials involving more than 6,200 children and adults, researchers concluded that dermatologists should not routinely prescribe antihistamines as a way to manage eczema-related itchiness, addressing “a longstanding uncertainty” about the role of these drugs in treating this inflammatory skin condition.
“Our systematic analysis of the best available evidence found that antihistamines do not provide enough improvement in eczema or itch for most people to notice an important difference,” says senior author Derek Chu, MD, PhD, chair in allergy for the Canadian Institutes of Health Research at McMaster University in Hamilton, Ontario, and lead of Canada’s Allergy Clinical Trials Network.
Antihistamines (such as diphenhydramine, chlorpheniramine, and hydroxyzine) also do not clearly improve sleep or prevent flare-ups, and they may cause side effects such as drowsiness, Dr. Chu says.
“The findings suggest that eczema treatment should focus on controlling the skin inflammation, rather than routinely adding an antihistamine,” he says.
In the United States, around 31.6 million people (roughly 10 percent of the population) have some form of eczema, according to the National Eczema Association.
The condition is characterized by intense itching, which can disrupt sleep, physical activity, daily functioning at work or school, mental health, and social relationships.
Why Do Dermatologists Prescribe Antihistamines for Eczema?
Dermatologists began prescribing antihistamines for eczema because these medications can help with itchy allergic conditions, such as hives and bug bites, says Chu.
“Over time, this became a common treatment habit, despite uncertainty if they were helpful,” he says.
Because itching is often triggered by histamine (a chemical in the body associated with immune responses), dermatologists had reason to think that antihistamines could effectively subdue the itching caused by eczema.
Doctors also prescribed antihistamines because of their sedating effects, hoping to help patients combat nighttime itchiness by inducing sleep, according to Clinton Dunn, MD, an allergist based in Norfolk, Virginia, and vice chair of the American College of Allergy, Asthma, and Immunology’s Dermatology Committee.
As research continued, however, it became more clear that histamines were not responsible for itching related to eczema.
“This study validates where atopic dermatitis [eczema] care is going, with an emphasis on understanding the actual mechanisms,” says Dr. Dunn, who was not involved in the research. “The current understanding is that the itch related to atopic dermatitis is through a signal between the cells of our body called cytokines.”
A Closer Look at Cognition-Related Antihistamine Side Effects
The scientific review by Chu and his collaborators highlighted that modern, second-generation antihistamines, commonly known under brand names such as Reactine, Claritin, Aerius, Allegra, Rupall, and Blexten, produced small changes in eczema severity and itch, but that relief fell short of what patients and their clinicians would consider as an important improvement.
The researchers also found that earlier first-generation antihistamines, commonly sold under brand names such as Benadryl, Chlor-Tripolon, and Polaramine, produced no noticeable improvement.
These older medications were also likely to increase cognitive impairment, such as drowsiness, confusion, slowed thinking, or diminished school or work performance, according to the study authors. “Some of these older first-generation antihistamines have also been linked to long-term cognitive impairment and dementia,” says Chu.
Cognitive effects from second-generation antihistamines were much lower and differed by drug (bilastine, desloratadine, and fexofenadine being the least sedating).
Research Analysis Could Lead to Guideline Changes
Many allergy and dermatology specialists already recognize that antihistamines often do not adequately address the underlying inflammation that drives eczema.
Saira Q. Zafar, MD, an allergist and immunologist with Schweiger Dermatology & Allergy in Millburn, New Jersey, was not surprised by the research findings. She praised the study, however, for its extensiveness and analysis of different types of antihistamines.
“The investigators reviewed 47 randomized controlled trials and used established approaches to evaluate the quality of the evidence,” says Dr. Zafar, who was not involved in the research. “A limitation is that they included studies varied in design, patient populations, and treatments, but which is common in systematic reviews.”
She mentioned that antihistamines should not be ruled out for all eczema patients, as some patients may have other allergic conditions, such as allergic rhinitis or hives, where these drugs may be helpful.
Existing guidelines have been inconsistent in terms of whether they recommend for, against, or make no recommendation at all about the role of antihistamines in eczema, notes Chu.
He suggests that recommendations from the American Academy of Allergy, Asthma, and Immunology/American College of Allergy, Asthma, and Immunology will be updated due to this latest comprehensive analysis.
“Antihistamines may be useful for hives, hay fever, or another separate allergic condition, but they should not replace proper eczema treatment [for] addressing skin inflammation,” says Chu. “People whose eczema remains itchy, disruptive, or poorly controlled should speak with their clinician or eczema specialist about treatments that directly address the disease.”
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