The Advertising Standards Authority (ASA) has banned adverts for two health clinics after they promoted the benefits of Botox.
Advertising prescription-only medicines such as Botox is prohibited under UK regulations.
The ASA said the rulings against Dermaskin Clinics, based in Cardiff, and HB Health of Knightsbirdge "set a precedent of what we expect from all advertisers across the sector" and would be followed up by compliance work. The watchdog said:
"It is illegal to advertise a prescription-only medicine, such as Botox, to the public. Our rulings, which apply to ads across media including online, set a clear precedent for the whole health and beauty sector.
"Any company referring to Botox must stick to the facts and avoid any promotional language. We'll be communicating this requirement to the sector and providing help and advice so they get their ads right."
NICE has been considering whether the injection should be offered across the NHS in England and Wales.
It has estimated the cost to the NHS would be £349.40 for every 12-week cycle of treatment.
Chronic migraines - believed to affect 1.6% of adults - involve having headaches for at least 15 days a month over three months, eight of which are migraines.
It is not known exactly why Botox may work for migraine although it is thought it may block pain signals as well as being a muscle relaxant.
Botox treatment has revolutionised the lives of many patients where other treatments didn't work. Joanna Hamilton-Colclough, who is director of the Migraine Action charity, says it's a cost effective treatment that should be made available on the NHS.
Joanna has suffered from chronic daily headaches since childhood. She says having the Botox treatment has transformed her working life and left her pain free for the first time in 30 years.
Technology Evaluation Centre at NICE, said:
The use of Botox to treat chronic migraine on the NHS moved a step nearer today.
Health watchdog the National Institute for Health and Clinical Excellence (NICE) has published final draft guidance which recommends the anti-wrinkle jab for the condition.