Nettle is particularly effective as a diuretic, so it helps
prevent most types of kidney stones as well as urinary tract infections. By keeping water flowing through the kidneys and bladder, nettle helps keep crystals from forming into stones and washes bacteria away.
Nettle is distinctly different from diuretic drugs. These drugs are often used to reduce high blood pressure and edema (swelling from excessive fluid), but studies have not shown nettle to help either of these conditions. It's unclear why this is the case. It may be that the herb works differently than diuretic drugs, or it may simply be that the correct research has not yet been done.
Nettle leaves can also help reduce the pain of arthritis. In one preliminary study, nettle leaf juice was as effective at reducing the pain of various types of arthritis as anti-inflammatory drugs. In another study, nettle leaf juice enhanced the effects of the anti-inflammatory drug diclofenac in people with osteoarthritis.
In addition to drinking nettle leaf tea or juice, an old tradition for relieving the pain of arthritis is to apply fresh leaves over aching joints. Though this initially causes increased pain from the stings, it ultimately relieves inflammation and pain. This effect may be the result of something known as the "gate phenomenon."
When the skin over a painful joint is stung, the spinal cord reduces pain signals coming from the joint underneath. Two studies have now shown that the application of topical nettle stings is in fact helpful for relieving arthritis pain for those who can tolerate the initial discomfort. Taking nettle by mouth in any of its forms, including capsules or tinctures, is also helpful for arthritis.