Stimulated by Pan et al 2021,[1] and Li et al 2021.[2]
SCD – systemic contact dermatitis
key to acronyms
EA – electroacupuncture
IgE – immunoglobulin E
GRPR – gastrin-releasing peptide receptor
DYN-A – dynorphin A
We have all heard of allergy to metals in the form of a localised dermatitis at the site of contact, often from jewellery or a metal watch strap for example. We have also heard that such allergy can result in skin reactions to acupuncture needles, but this has been reported very rarely. I guess this is rare because of the limited contact time with the metal during acupuncture treatment.
I don’t think I had come across a systemic form of contact dermatitis before seeing this recent paper from Beijing. I guess this is a very rare event, partly because it comes from a unit devoted to ‘Complex Severe and Rare Diseases’.
The patient was a 70-year-old woman receiving EA for recurrent urticaria. She developed erythema at the site of treatment after a week, but then a very itchy maculopapular rash appeared on her limbs and spread to her entire body. The rash did not respond to antihistamines or corticosteroids. Her IgE levels were markedly elevated but specific IgE to common allergens were all negative. Skin biopsy was not diagnostic, showing a perivascular lymphocytic infiltrate in the entire dermis with large numbers of eosinophils. She had an enlarged cervical lymph node, but sensibly refused a biopsy.
She was initially misdiagnosed with bulous pemphigoid and hypereosinophilic syndrome, but following patch testing she showed reactions to chromium and cobalt, and some fancy testing of the stainless steel needles confirmed the presence of these metals, and the fact that they were increased in artificial sweat in contact with a needle.
The paper has a nice graph of total IgE and eosinophil count over a 4-year period. Both fall in the first 6 months after the EA was stopped, and stay at a normal level for 3 years follow up.
Li et al is another paper I had on my list, which is related through both EA and itch. It is an experimental paper testing EA at different frequencies on a mouse model of dry skin pruritis. EA was applied from LI4 to LI11 at either 2, 15 or 100Hz for 30 minutes every other day for a total of 5 sessions.
100Hz EA was best in relieving chronic itch
To my surprise the 100Hz EA proved to be by far the best frequency in relieving chronic itch, and this appeared to be associated with a reduction in the expression of GRPR (which was increased in the model) and an increase in expression of DYN-A in the cervical dorsal horn (which was reduced in the model).
The increase in dynorphin from high frequency EA is consistent with the laboratory research of Jisheng Han in pain.[3,4] Subsequently the role of dynorphin in itch suppression has been established,[5] and the results of this paper seem entirely consistent.
Will I have to change my practice?
It looks as though I will have to consider changing my practice to reinstating high frequency EA under some special itchy circumstances.
References
1 Pan Z, Dong J, Sun J, et al. Systemic contact dermatitis caused by acupuncture – a neglected route of allergen entry. Contact Dermatitis Published Online First: 27 January 2021. doi:10.1111/cod.13796
2 Li H-P, Wang X-Y, Chen C, et al. 100 Hz Electroacupuncture Alleviated Chronic Itch and GRPR Expression Through Activation of Kappa Opioid Receptors in Spinal Dorsal Horn. Front Neurosci 2021;15:625471. doi:10.3389/fnins.2021.625471
3 Han JS, Xie GX. Dynorphin: important mediator for electroacupuncture analgesia in the spinal cord of the rabbit. Pain 1984;18:367–76.
4 Han J-S. Acupuncture: neuropeptide release produced by electrical stimulation of different frequencies. Trends Neurosci 2003;26:17–22. doi:10.1016/S0166-2236(02)00006-1
5 Kardon AP, Polgár E, Hachisuka J, et al. Dynorphin Acts as a Neuromodulator to Inhibit Itch in the Dorsal Horn of the Spinal Cord. Neuron 2014;82:573–86. doi:10.1016/j.neuron.2014.02.046
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