Been doing a lot of digging on glucosamine due to recently developing osteoarthritis.  Came across some information suggesting it might prevent or reduce the frequency/severity of clusters.

Glucosamine for migraine prophylaxis?
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A brief article from 2000 that mentions both migraines and clusters.  Started with observations/correlations between taking glucosamine and fewer migraines, went on to a small trial on 10 patients, with decent results.

Effect of glucosamine on the degranulation of mast cells and ear swelling
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Lab study that showed that glucosamine reduces the nasty tendency of mast cells to drop little histamine and serotonin bombs at the wrong moment... these are associated with the redness and swelling on the affected side. Also mentions that calcium mobilization is less overactive when taking glucosamine. Blocking calcium channels is how verapamil works ... not aware of any interactions between verapamil and glucosamine as they seem to work on different mechanisms, but due diligence is advised before adding anything to verapamil regimens.

Glucosamine is unlikely to be a miracle treatment, but it is relatively safe and inexpensive, and might lead to a reduction in pain.  It works differently than many other OTC methods (melatonin, magnesium, antihistamines,  taurine, etc), so it might strengthen such an approach. And if you are getting old and arthritic like me, its worth considering just for creaks and pops.