Another very common example is a person who is allergic to nickel and breaks out in an itchy rash from earrings, a watch, or the metal buttons and snaps on pants. Allergic contact dermatitis can even be work related. An example would be a construction worker who is allergic to the cement he is working with all day and is forced to change jobs. While all the mechanisms leading to the rash are not clear, we do know that the body has an exaggerated reaction which causes the skin to become hyperactive. In other words, the immune system is overactive in the skin and a rash ensues.
Marijuana is derived from the hemp plant, which is also used to make clothes and rope, in addition to its psychoactive and medicinal purposes. The active elements of marijuana are the cannibinoids, which are responsible for its effect on the human mind and body. In recent years, scientists have discovered that these cannibinoids bind certain receptors in the body and brain, and that our bodies naturally make chemicals that are very similar to the cannibinoids from the marijuana plant.
The two main receptors from the marijuana plant are termed CB1 and CB2, and the naturally occurring cannabis like chemicals in the human body are called anandamide (found in the brain) and 2-AG (from the intestine).
Their effects are numerous, and as a result, these receptors have theoretical uses in cases of multiple sclerosis, spinal cord injury, pain, inflammatory disorders, glaucoma, bronchial asthma, vasodilatation that accompanies advanced cirrhosis, and cancer.
The CB-1 and CB-2 receptors, for example, have been linked to appetite, and they can potentially be used to increase the appetite of emaciated cancer patients.
CB-1 and CB-2 have also been linked to pain alleviation, and their use can be easily justified for cancer patients or people with a painful condition of the pancreas called pancreatitis. Several years ago, scientists discovered their potential use for Alzheimer's Disease prevention.
Until recently, dermatologists would be hard-pressed to find a reason to suggest that a patient use cannabis for his or her skin. However, several months ago, scientists tested a mouse with hypersensitive skin to show the potential use of marijuana in allergic contact dermatitis.
Mice are a useful investigative tool in science because their genes can be manipulated, and at the gene/cell level people and mice are remarkably similar. For this reason, experiments are performed on mice and their conclusions are usually assumed safe for testing on humans.