Two British universities are looking for couples to volunteer for a "groundbreaking" trial of a male contraceptive gel.
Eighty adult men under the age of 50 who are in a stable relationship with an adult woman under 34 are being recruited by the University of Manchester and the University of Edinburgh.
For the next two years, they will be asked to use a daily gel as "their sole method of birth control" and attend a clinic monthly to monitor their sperm count.
The gel, called NES/T, is a hormone-based treatment designed to reduce sperm production without affecting libido. It is to be applied to the upper arms and shoulders.
'Safe and simple way'
Condoms and vasectomies are currently the only forms of contraception available to men. While condoms are over 98% effective at preventing pregnancies when used correctly, their effectiveness is, in reality, closer to 85%, according to the American NGO Planned Parenthood.
The contraception burden has therefore mostly fallen on women but many experience unpleasant side effects upon taking the pill including headaches and migraines, mood swings and weight gain — although Britain's health service, the NHS, said there is no evidence linking the pill to weight gain.
Additionally, the pill is not recommended for women over the age of 35 who smoke or women with certain medical conditions.
Researchers hope the male contraceptive gel could be a sustainable alternative method for couples.
"We believe this preparation will allow men to control their fertility in a safe and simple way," Dr Cheryl Fitzgerald, Consultant Gynaecologist at Saint Mary's Hospital and Manchester University said in a statement.
Research into other methods of male contraception has been ongoing for several years.
A hormonal injection to be carried out every eight weeks was found to be 96% effective but the one-year trial was stopped by World Health Organization in 2016 to address the reported side effects which included acne, mood swings, muscle pain and increased libido.
"Previous trials have shown that hormonal contraception for men can be safe and effective," Professor Richard Anderson from the University of Edinburgh's MRC Centre for Reproductive Health said in the statement.
"This trial allows men to self-administer a gel, which may be more convenient and acceptable than needing repeated injections, as was the case with previous trials," he added.
The gel, like most contraceptive methods excluding condoms, would not prevent the spread of sexually-transmitted disease.