Histamine is a natural chemical produced by the immune (disease-fighting) system of the body. When it is released, it increases blood flow to the affected area. Liquid leaks out of the blood vessels, making the mucous membranes lining the nose and throat to swell, and stimulating nearby gland to produce mucus. It causes symptoms such as itching, swelling, or reddening. Histamine can also cause sneezing, running nose, itchy or watery eyes, and in some people can cause breathing difficulties.

Histamine is involved in a variety of physiologic responses, such as inflammation, type I allergy, gastric acid secretion, and neurotransmission.

Natural Supplements that have antihistamine action
There are quite a number of herbs that have shown natural antihistamine action in lab studies, however few human trials are available to tell us how effective these "herbal antihistamines" are work when ingested as a supplement. I will present a few options but keep in mind that this is by no means an endorsement of these herbs. I just want people to know that there are some herbs that have potential and hopefully future research will give us some additional clues about natural antihistamine herbs and nutrients.

Butterbur is a supplement available orally

Mangosteen is a fruit extract supplement usually sold in juice form or as capsules.

For more information on natural antihistamines, see allergy or allergic rhinitis

Antihistamine Drugs
Antihistamine drugs are used to stop the effects of histamine, most often used to stop a runny nose or skin allergy. Antihistamine drugs are most often used to treat allergic reactions, although certain types can be used in the treatment of other conditions such as migraines, travel sickness, and stomach ulcers. Antihistamine drugs are available as tablets, creams, and injections. There are over the counter antihistamine drugs and also antihistamine drugs by prescription. The older antihistamines, such as Benadryl, tend to cause drowsiness and rare dangerous heart arrhythmias (terfenadine and astemizole). More recently developed, new antihistamines, cause less drowsiness but may still cause heart rhythm problems. It is difficult to mention the best antihistamine since each person will have their own preference.

Antihistamine side effects
Antihistamine medications can produce some unpleasant side effects. Common antihistamine side effects include drowsiness, dry mouth, difficulty in urination, and constipation. An antihistamine overdose could cause excessive sedation and heart rhythm irregularities. The newer non drowsy antihistamines are an option for those who need to take antihistamines during the day. However, I suggest using antihistamines medicines as little as possible to reduce the potential side effects. It is probably best not to use an antihistamine during pregnancy unless absolutely required.

Antihistamine and Decongestant
Many products on the market have an antihistamine and decongestant combined. I think these pills may be appropriate for those who have nasal allergies, but a combination antihistamine and decongestant is not appropriate for treating the common cold since there is no allergy involved in the common cold.

Metabolism of histamine
Histidine decarboxylase (HDC), is the rate-limiting enzyme for mammalian histamine synthesis. Histamine is a multifunctional biogenic amine with relevant roles in intercellular communication, inflammatory processes and highly prevalent pathologies. Histamine biosynthesis depends on a single decarboxylation step, carried out by a PLP-dependent histidine decarboxylase activity.

Metabolism of histamine from food
Histamine is a biogenic amine that occurs to various degrees in many foods. In healthy persons, dietary histamine can be rapidly detoxified by amine oxidases, whereas persons with low amine oxidase activity are at risk of histamine toxicity. Diamine oxidase is the main enzyme for the metabolism of ingested histamine. Some people may have histamine intolerance if they cannot breakdown histamine from foods fast enough.

Natural Antihistamine Research Update
Inhibitions of histamine release and prostaglandin E2 synthesis by mangosteen, a Thai medicinal plant.
Biol Pharm Bull. 2002 Sep;25(9):1137-41.
The fruit hull of mangosteen, Garcinia mangostana L. has been used as a Thai indigenous medicine for many years. However, the mechanism of action of mangosteen as a medicine has not been elucidated. The present study was undertaken to examine the effects of mangosteen extracts (100% ethanol, 70% ethanol, 40% ethanol and water) on histamine release and prostaglandin E2 synthesis. We found that the 40% ethanol extract of mangosteen inhibited IgE-mediated histamine release from RBL-2H3 cells with greater potency than the water extract of Rubus suavissimus that has been used as an anti-allergy crude drug in Japan. All extracts of mangosteen potently inhibited A23187-induced prostaglandin E2 synthesis in C6 rat glioma cells, while the water extract of Rubus suavissimus had no effect. The 40% ethanol extract of mangosteen inhibited the prostaglandin E2 synthesis in a concentration-dependent manner with relatively lower concentrations than the histamine release. In addition, passive cutaneous anaphylaxis (PCA) reactions in rats were significantly inhibited by this ethanol extract as well as by the water extract of Rubus suavissimus. These results suggest that the 40% ethanol extract of mangosteen has potent inhibitory activities of both histamine release and prostaglandin E2 synthesis.

Natural Antihistamine questions
Q. Hi Dr. Sahelian ,I always read your website about all of the products that you talk about, and I find it very informative. I was wondering if you knew anything about Histadelia, a disorder characterized by high histamine levels. I was wondering if you knew anything about it, and if so, then what supplements or nutrients would you recomend taking? Whenever I search for "Histadelia" on the net, I always seem to run across another keyword: "pyroluria". If you could help me out with these questions, I would be very grateful!!!!
     A. I have not studied histadelia or pyroluria, but if you do a search on google and find out all the web pages where histamine is mentioned. Try these words in google: histamine site:raysahelian.com

Q.  i recently bought a book called 'The complete guide tp vitamins herbs and suppkements' by winifred conkling w/ david  y. wong, m.d., consulting editor. In it concerning impotence it said some over-the counter antihistamines and decongestants can cause temporary impotence, but can they also cause testosterone levels to drop ,if so can the effects of long term use of these be reversed ?.
     A. It is true that in some people decongestants and antihistamines can cause impotence, but it is unlikely that it is due to testosterone. Many people find sexual enhancement with herbs and supplements that can reverse this condition.

Q. I get an allergic response (sinus problems, skin rash) to oral carnosine at 500-1000mg.  I believe it's a histamine release but I find it strange.
     A. Carnosine converts into histidine which converts into histamine. Perhaps too high of a carnosine dose can shift the metabolic pathway towards histamine.

Q. I have found an antihistamine to be a very effective sleeping pill without hangover and I don't think there's addiction. Is there any problem with taking antihistamines for sleep? How about for a long period or time?
     A. Most drugs have side effects. Long term antihistamine use can lead to tolerance, but whether the older antihistamines have cardiac effects in the long run is difficult to tell at this time. The newer H2 blockers may have cardiac side effects.