Histamine is best known as a part of the defense against allergies. But it is also an important neurotransmitter – a brain chemical involved in arousal, anxiety, the stress-related release of hormones, activation of the sympathetic nervous system, pain relief, and other functions.
Increased sensitivity to histamine may lead to an excessive allergic reaction which is relieved by anti-histamine drugs. It can also increase pain. One strategy thought to reduce this over-reaction is desensitization – injecting small amounts of histamine which can lead to a reduced reaction.
This approach seems to help some migraine and cluster patients. It was first reported in 1941 by a Mayo clinic doctor, Bayard Horton in an article entitled The use of histamine in the treatment of specific types of headaches. Another article, Intravenous histamine in the treatment of migraine was published in 1946 by W.A. Thomas and S. Butler.
A group of Mexican doctors compared subcutaneous (under the skin) injections of small doses of histamine to injections of placebo in 60 patients. They found histamine to be more effective. The same group of doctors conducted three more double-blind trials of histamine injections. A double-blind study of 90 migraine patients compared twice-weekly injections of histamine with 100 mg of oral topiramate, which is an FDA-approved treatment for migraines. These treatments were equally effective. They then compared twice-weekly injections of histamine to 500 mg of valproate, which is also an FDA-approved migraine drug in 92 migraine patients. Histamine was superior to valproate. They compared histamine to the injection of a relatively small dose of Botox (50 units, while the standard dose is155 units) in 100 patients and found them to be equally effective.
These results would be more convincing if another group confirmed these findings. When I asked the opinion of an allergy specialist in NYC, Dr. Michael Chandler he told me that the idea of histamine desensitization has been discredited and that it is not being used to treat allergies.
