Histamine is a chemical produced by your immune system. A specific antibody -- IgE or immunoglobin E -- binds with mast cells and leukocytes, especially in the respiratory system. When IgE comes in contact with an allergen such as dust or pollen, it causes the mast cell or leukocyte to produce histamine. Histamine triggers inflammation, causing capillaries to open -- vasodilation -- which makes tissues swell. It also increases fluid secretion and stimulation of nerve endings in the skin.
Highly Trained Athletes
In a study published in 1999 in "Medicine and Science in Sports and Exercise," seven young highly trained endurance athletes and seven older highly trained endurance athletes were compared with seven young and seven older untrained men. Blood samples were drawn during incremental exhaustive exercise. Both the younger and the older athletes showed higher levels of histamine release than did the untrained men. This result seems to be an effect of high-level training, as exercise did not induce the release of as much histamine in the untrained men while they were exercising.
Effects of Histamine
Histamine triggers inflammation. One of the actions of inflammation is increased permeability of blood vessels. Blood fluids squeeze out of blood vessels and saturate the tissues, causing swelling. It also causes smooth muscle cells to contract. The respiratory tract and lungs are lined with smooth muscle cells, and when they contract in response to histamine release, breathing becomes difficult. In highly trained athletes, this produces exercise-induced asthma during or after training exercises or competition. Swelling of tissues in the sinuses, respiratory tract and lungs makes the problem worse.
Allergies
You always have some histamine circulating through your body. When you are exposed to allergens such as dust, pollen, toxic plants like poison ivy or toxic chemicals from an insect bite, your body produces large amounts of histamine, causing all the symptoms of inflammation. Athletes who train outside for hours are exposed to more allergens than they likely would encounter in ordinary activities. This, combined with the increased level of histamines produced in response to intense exercise, increases the amount of allergy attacks that athletes experience.
Theories
Histamine causes vasodilation, capillary permeability, swollen tissues, constriction of airways, stimulation of mucus secretion and itching and pain in the skin. Excessive amounts of histamine are also associated with lower blood pressure, which causes athletes to faint after exercise. A 2006 article on the ScienceDaily website reported that scientists at the University of Oregon conducted studies with highly trained athletes, giving them antihistamines 60 minutes before they exercised. Taking the antihistamines seemed to act against the excessive histamine during exercise, so that the athletes didn't have such a severe drop in blood pressure after exercise and didn't faint. This does not mean that athletes should begin taking antihistamines before exercise. Consult your sports medicine doctor about the advisability of doing this.
References
- Medicine and Science in Sports and Exercise:: Basophil Releasability in Young Highly Trained and Older Athletes
- Brown University Health Education: Hay Fever
- ScienceDaily: Finding May Explain Biggest Cause of Post-Exercise Fainting
- Duquesne University Regenerative Medicine: The Functions of Histamine
- University of California: White Blood Cells in Lung Produce Histamine Seen in Allergies
- Community College of Baltimore County: The Adaptive Immune System
- Medicine and Science in Sports and Exercise: Interleukins 1-beta, -8 and Histamine Increases in Highly Trained, Exercising Athletes
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