If the tests are successful, allergy charities hope the treatment, to be administered with an inhaler, will dramatically help sufferers of the often-debilitating respiratory condition.
Besides hayfever, the treatment will stop the symptoms of asthma from developing but without any serious side effects.
"A lot of people out there with asthma are not happy with the current therapy. This could be very big both medically and financially," the Daily Express quoted Clive Page, professor of pharmacology at King's College London, as saying.
"The current inhalers can have debilitating side-effects. We hope this will give people the same kind of cover but without the side-effects. This is a better way of treating the underlying effects of the diseases and we are cautiously optimistic," Page added.
The drug compound is being hailed as a big step forward in the treatment of asthma and hayfever because it does not involve steroids or other compounds that can have side effects.
The compound, RPL554, is the invention of Sir David Jack, the former research director of GlaxoSmithKline, who developed some of the main respiratory drugs in use today, including the asthma treatment Ventolin.