Causes of Histamine Swelling

Swelling, also called edema, is any enlargement of the body. Organs and skin typically swell when there is an abundance of fluid in the tissue. Swelling can occur in a single area (such as your ankles) or can affect the whole body. Many factors can cause swelling, among them injury, sunburn, poor nutrition, too much salt in your diet, organ failures or diseases (especially dealing with the kidney, heart or liver) and as a side effect of some drugs. But many everyday instances of swelling are caused by a histamine reaction to an allergen.

Histamine

• Histamine is produced by basophils and mast cells as an immune response to some invader (or pathogen), often an allergen. A rapid inflammation response is triggered in which histamine production dilates area blood vessels. These dilated vessels or capillaries become abnormally permeable, allowing white (infection-fighting) blood cells access to the invader.
  Cellular histamine receptors are associated with basophils and mast cells found throughout the body. Histamine reactions (including swelling) are generated by the effect of histamine on a particular histamine receptor.

H1 Histamine Receptor

• The H1 histamine receptors are found on smooth muscle, in central nervous system tissue and in endothelium--the thin, cellular lining on the inside of blood vessels. The various reactions of histamine on the H1 receptor include sinus swelling, rashes, and pain and itching due to insect stings. The latter often includes swelling. In short, the H1 receptors are generally responsible for allergic reactions.

Allergies

• Allergies cause the production of histamine. In turn, the body reacts. In mild allergic reactions, the histamines, in combination with histamine receptors, may produce rashes, itchy and watery eyes, and congestion--a combination of mucus and swelling in the sinus cavity.
  In more moderate reactions, the airways may tighten (swell) causing some difficulty breathing. But the most severe allergic reaction is anaphylaxis. Anaphylaxis is a life-threatening reaction which affects the body globally. Generally, the airways constrict or swell, making breathing exceedingly difficult, and there is a sharp drop in blood pressure. Other symptoms, such as vomiting, cramps, diarrhea and mental confusion, may also be present.

Insect Stings

• A common cause of swelling is from insect stings--most especially those from bees, wasps, hornets, yellow jackets or fire ants. Both normal and allergic reactions can produce swelling. In a normal reaction, the sting area itself will swell and be painful. As well, it will probably be red and itchy. Even should a larger area swell, the reaction could be normal--and in such an instance would be called a "large local response." For example, if you were stung on the hand, the entire hand or part of the forearm could swell in response.
  With an allergic reaction, in which histamine is released, there will be additional symptoms. You will likely have difficulty breathing as airway passages are swelling, possibly causing wheezing. Your face, throat or mouth may swell, though the sting was not in that vicinity, making it difficult to swallow. A rash (or hives) could spread to areas beyond the sting site. You may feel dizzy, or anxious, or faint. Your heart may beat rapidly.

Antihistamines

• Antihistamines are not produced naturally by the body, but are a drug taken to combat the effects of histamine on the histamine receptors. So while the body will continue to produce histamines, the effects (itchy eyes, rash, swelling, etc) will be reduced. They work by blocking the messages sent by histamine to the histamine receptors. Commonly used H1 blocker antihistamines include Benadryl, Claritin, Chlortripalon, Atarax, Hismanal and Seldane.