People who have never been exposed to poison ivy are indeed immune. The skin contains a special enzyme which binds to urushiol, the oil found in poison ivy. However, each time this enzyme binds to the oil, the amount of enzyme in the skin decreases. The body does not replenish this enzyme after birth. Therefore, after coming in contact with urushiol enough times, you will have depleted your ability to block the absorption of the urushiol into the skin. Hence you become allergic to poison ivy. Different people are born with different amounts of this enzyme present in their skin. Therefore, it can seem as if a person is immune after years of touching it. However, given enough contact, everyone will become allergic on a certain level.
Once the urushiol is absorbed into the skin your immune system recognizes the oil as a foreign substance and instructs your white blood cells into the area to attack the foreign substance. Since the oil is embedded in the skin now, the white blood cells attack the 'infected' skin and destroy everything causing severe tissue damage. By itself urushiol is completely harmless.
Some people claim that constant exposure to poison ivy can create immunity. This is incorrect, your immune system is very active fighting off day to day infection and bacteria, if it can not spare T cell fighters it will not attack the oil and you will have no reaction. People with Aids or serious infections who have considerable white blood cell shortages are known to be completely immune to urushiol because their body can not spare extra white blood cells to attack the oil.
In conclusion, if you think you are immune, rest assured, if you touch it enough, you will get poison ivy.
|
