We pay a good deal of attention to the intersection of allergies and sleep disturbance around here, and it has popped up again.
Years ago I co-wrote a book called Sleep to Save Your Life with sleep specialist Dr. Gerard T. Lombardo that had a chapter called “Restless Legs—Pain in Motion.” I had never heard of it till I worked with Dr. Lombardo, but I can’t forget it. The chapter began with an account of a patient who disobeyed the instructions to bring all his accustomed props to the sleep lab for an overnight study because he was embarrassed to bring a piece of wood the size of a baseball bat and use it to pound his legs while hooked up to electronic monitors under the gaze of a video camera. Restless leg patients frequently resort to inflicting pain on themselves to relieve the pain from within—described variously as aching, burning, cramping, and “creepy crawly” sensations as from bugs or worms. Clearly, this is not Steve Martin’s “happy feet.”
By coincidence, just about the same time we worked on the book, commercials started popping up on TV for a drug to treat it. Since most of my friends had never heard of the ailment restless leg syndrome, or RLS, they tended to dismiss it as one more contrivance by the pharmaceutical industry to monetize an annoying but not serious problem. That drug no longer seems to pop up on TV.
However, RLS has not gone away. The American Sleep Association estimates that it afflicts 12 million Americans. An article that popped up in my news feed the other day mentioned that William Ondo, M.D., a Houston Methodist neurologist, thinks it’s a bigger problem for those with seasonal allergies. Double jeopardy may be impermissible as a matter of law, but for those with RLS, symptoms get worse during allergy symptoms if patients take diphenhydramine—Benadryl–and other first-generation antihistamines at night, drugs that are normally sedating (do not drive or operate heavy machinery).
The reason that Benadryl is sedating for most of us is precisely because it passes the brain-blood barrier where it suppresses brain histamine, a neurotransmitter that is at high levels during the day and crucial for keeping us alert. It down regulates at night, allowing us to sleep. But with RLS it seems to have a paradoxical effect.
Apparently RLS is fairly common among kids with atopic dermatitis: “Awakenings as a result of scratching can be brief or long, and many children with AD have a comorbid diagnosis of restless leg syndrome apparently secondary to itch-induced movements. Restless leg syndrome is diagnosed clinically as an unrelenting urge at night and before sleep onset to move the legs. Children with AD are also often given a diagnosis of periodic leg movement disorder, which is defined by the presence of repetitive limb movements that, in contrast to restless leg syndrome, only occur during sleep and not before sleep onset.”
What a drag. Parents resort to Benadryl to relieve their children’s maddening itching at night when cortisol levels are low, and get blindsided by RLS.
For these children, newer, non-sedating antihistamines such as loratadine [Claritin] and cetirizine [Zyrtec] are preferable to Benadryl. According Ondo, “We don’t yet understand why sedating antihistamines worsen restless legs syndrome, but we do know that non-sedating antihistamines do not affect the symptoms as much because they do not enter the brain as easily.”
I posed this problem to our contributor, Jessica Dabler Martin, PhD neuroscientist who found a 2009 article that elucidates some of the research on histamine and RLS, which is inconclusive on the specific pathways involved. She observes, “I’m just amazed at how little this has been looked at even though the association has been there for some time! The study referenced from Hopkins was a poster abstract at a neuroscience meeting from 2008, but it appears they never went on to fully publish the results.
“Once again, all of this shows that the same molecule – histamine in this case – can have many different functions throughout the body. The nervous and immune systems overlap yet again.”
So, once again sleep disturbance and allergies collide. Poor sleep takes the fun out of waking life, not to mention overall good health. There’s a good reason that sleep deprivation is a form of torture.