Researchers have found in animal trials that a compound called tetrahydrocannabinol (THC), which is naturally occurring in Cannabis sativa (otherwise known as marijuana) can reduce allergic skin reactions.

For example, he exposed the ears of mice with normal endocannabinoid receptors to a chemical irritant called dinitrofluorobenzene (DNFB), which causes a severe skin reaction similar to that caused by poison ivy in humans.

Within a matter of minutes, the amount of an endocannabinoid called anandamide jumped from undetectable levels to about 300 picomoles per gram of analysed tissue.

When Zimmer's team applied 30 micrograms of synthetic THC to the animals' ears it reduced the skin irritation by half. For comparison, a cannabis cigarette contains as much as 150 milligrams of THC.

Such endocannabinoids may also produced by the body and speculates that individuals with (autoimmune) inflammatory conditions such as asthma and eczema may might not produce enough such endocannabinoids. In these cases, THC-like compounds may have therapeutic potential.

BUT, do not try to self-medicate with marijuana!

Should you require further reading, the study has been published in Science (DOI: 10.1126/science.1142265).