Question: How many people are sensitive to histamines?
About the article "Yeast", section "Wine".

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Red wine has 20–200% more histamines than white wine, and those who are allergic to them are deficient in a certain enzyme.
Some experts believe that the combination of alcohol and that deficiency could cause headaches.
However, a study of 16 people with an intolerance to red wine, reported in the "Journal of Allergy and Clinical Immunology" (Feb 2001), found no difference in reactions to low and high histamine wines.
Taking loratadine (Claritin) an hour before drinking should reduce the reaction to histamines and the resulting symptoms.
This would tell an individual whether histamines were the cause of their problem. 
The symptoms are thought to be caused by mast cells in the surface of the skin releasing histamines without the presence of antigens, due to the presence of a weak membrane surrounding the mast cells.
The histamines released cause the skin to swell in the affected areas.  
Histamine-directed medications.
"Based on the role of histamine in keeping people awake (and hence the common side effect of anti-histamines such as diphenhydramine causing sleepiness), medications that act on histamine are under development for the treatment of excessive sleepiness."
It remains to be seen whether or not these H3 antagonists (i.e., compounds such as pitolisant that promote the release of the wake-promoting amine histamine) will be particularly useful as wake-promoting agents. 
Allergies are an abnormal immune reaction.
The human immune system is designed to protect the body from potential harm and in people who have allergies the immune system will react to allergens (substances that trigger an immune response).
The immune system will produce immunoglobulin E, IgE, antibodies for each allergen.
The antibodies will cause cells in the body to produce histamines.
These histamines will act on different areas of the body (eyes, throat, nose, gastrointestinal tract, skin or lungs) to produce symptoms of an allergic reaction.
The allergic response is not limited to a certain amount of exposure.
If the body is exposed to the allergen multiple times the immune system will react every time the allergen is present.
The reason why people get allergies is not known.
The allergens are not passed down through generations.
It is believed if your parents have allergies the child is more likely to be allergic to the same allergens.
Some common symptoms include itchiness, swelling, running nose, watery eyes, coughing, wheezing, trouble breathing, hives, rashes, mucus production, or a more severe reaction anaphylaxis.
Allergic responses and the severity vary from person to person.
Many substances can trigger an allergic reaction.
Common triggers of a reaction include foods, likes nuts, eggs, milk, gluten, fruit and vegetables; insect bites from bees or wasps (often a severe response occurs); environmental factors such as pollen, dust, mold, plants like grass or trees, animal dander; medications or chemicals.
Some people experience an allergic response to cold or hot temperatures outside, jewelry or sunlight.
There are daily treatments to reduce the severity of the allergic response.
Often these treatments include an antihistamine oral pill, nasal spray, or eye drops.
Other treatments include an allergy shot, which keep the allergic response to a minimum.
For more severe reactions an epinephrine injection is carried around.
This injection will be taken if the person is going into anaphylactic shock.
The best treatment is avoidance of each allergen. 
Many species retain distasteful or poisonous chemicals acquired from their host plants.
Some species also have the ability to make their own defenses (Nishida, 2002).
Common defenses include: cardiac glycosides (or cardenolides), pyrrolizidine alkaloids, pyrazines and histamines.
Larvae usually acquire these chemicals, and may retain them in the adult stage.
But adults can acquire them too, by regurgitating on decomposing plants containing the compounds, and sucking up the fluid.
Adults can transfer the defenses to their eggs, and males sometimes transfer them to females to help with defense of the eggs.
Larval 'hairs' may be stinging, due to histamines the caterpillar makes, in some species but not all.
The insects advertise these defenses with aposematic bright coloration, unusual postures, odours, or, in adults, ultrasonic vibrations.
Some mimic moths that are poisonous, or wasps that sting.
The ultrasound signals help nocturnal predators to learn to avoid the moths, and for some species can jam bat echolocation.