The scientists believe that UV rays in sunlight cause nitrogen stored in the body to be released into the blood stream, relaxing blood vessels and lowering blood pressure.
However, excessive exposure to UV light is also known to be a major cause of skin cancer, so experts have warned the public against spendnig too much time in the sun unprotected.
Dr Richard Weller, a senior lecturer in dermatology at the University of Edinburgh who led the research, cautioned that more work needs to be done before they were able to offer advice to patients about using sunlight as a treatment for high blood pressure.
He said: “We now plan to look at the relative risks of heart disease and skin cancer in people who have received different amounts of sun exposure.
“If this confirms that sunlight reduces the death rate from all causes, we will need to reconsider our advice on sun exposure.
“We suspect that the benefits to heart health of sunlight will outweigh the risk of skin cancer.”
The researchers, who are presenting their findings at the International Investigative Dermatology Conference in Edinburgh, studied the blood pressure of 24 volunteers.
They were asked to spend 20 minutes under a UV tanning lamp, which allowed the dose of light to be controlled.
The scientists found while after receiving UV light, the volunteers’ blood pressure dropped and remained lower than before exposure for up to an hour.
When the volunteers were exposed to heat but no UV light from the tanning lamps, their blood pressure also dropped during exposure but then quickly increased back to previous levels.
Laboratory tests also showed that skin cells exposed to UV light released nitric oxide, a nitrogen based chemical that is known to cause blood vessels to relax.
UV from sunlight is known to have a number of benefits by helping the body produce vitamin D, but it is also the main cause of damage that causes skin cancer.