Allergic response 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 parents have allergies the child is more likely to be allergic to the same allergens. Some common symptoms include
Pollen calendar Pollen calendar A pollen calendar is used to show the peak pollen times for different types of plant pollen, which causes allergic reactions in certain people. A pollen calendar can be a very useful tool in forensic science, because it can be used to place the month, or week, or date of death. The use of pollen for criminal investigation purposes is called "forensic palynology". However, the use of a pollen calendar to set the date of death should be used with extreme caution, and only by a carefully trained expert witness. The CSI effect has put pressure on some