Histamine is one of the principal chemicals involved in the allergic response. It is responsible for many of the symptoms of allergy, including swelling, itchiness, and sneezing. It can also cause the overproduction of mucus, leading to a runny nose. This is the reason that anti histamines, drugs that block the action of this chemical, are often used in treating allergies. Other methods of therapy include nasal steroid sprays or cromolyn nasal sprays.
Common allergens are dust mites, proteins from pet fur called dander, molds, and pollen.
In some cases the item is obvious, as when cutting the grass or petting the dog provoke an allergic response. In others, the offending allergen may not be so easily identified or there may be many allergens, complicating the diagnosis and treatment of the problem. In many cases, conferring with an allergist can help sort out these issues. After a thorough history and physical examination, allergy testing may be warranted. Occasionally, allergy shots can help to blunt the individual's reaction to the allergen.