Chlamydia is a widespread problem in the UK
For the first time an antibiotic for chlamydia is to be made available from pharmacists, without a prescription.
People aged over 16 will be able to buy Clamelle after testing positive for the infection, or having sex with someone who tests positive.
The medicines regulator has decided the drug will be made available over-the-counter later this year.
If untreated, chlamydia can cause serious problems, including infertility in later life.
Experts are alarmed that rates of infection have soared in recent years, particularly among the young.
The drug, also called azithromycin, will still be available via the traditional route - either from a GP or a genito-urinary medicine clinic.
However, the Medicines and Healthcare products Regulatory Agency (MHRA) and pharmacists say the reclassification of the drug in the UK as an "over the counter" medicine will offer a more convenient alternative for some patients.
No-one will be able to simply walk off the street and buy the drug without some evidence they have chlamydia, or are likely to have it.
A letter giving the results of either a postal test kit, also available in certain pharmacies, or a test carried out in a surgery or clinic, will be needed.
The letter sent back from the manufacturers of the postal kit will include slips which can be torn off and handed to sexual partners, who can then produce these at pharmacies to buy their own supply of the antibiotic.
Dr June Raine, from the MHRA, said: "Chlamydia is the most common sexually transmitted disease in the UK, and up to 70% of people who have it have no symptoms and could therefore remain undiagnosed.
"We are keen to support the availability of more medicines over the counter, where it is safe to do so."
The move was supported by the Royal Pharmaceutical Society, the professional body for pharmacists.
Howard Duff, from the society, said: "Reclassifying azithromycin will expand on existing services and improve access to chlamydia screening and treatment for patients."
Natika Halil, from sexual health charity FPA, said that free testing and advice was still available from the NHS.
She added: "For people who are already testing themselves at home it is a really positive step forward that the treatment can now also be bought from pharmacies.
"This will ensure fast and effective access to treatment and has the potential to play an important part in reducing rates of chlamydia."