They promise services which guarantee new hair growth, or visible results after just one treatment session.
But such ads in the hair and beauty industry are bending the facts, and complaints against them are on the rise.
Singapore's advertising watchdog received 104 such complaints in the first 10 months of this year, compared with 78 in the whole of last year, and 40 in 2012.
The beauty industry has also received the greatest proportion of complaints between 2011 and last year, when compared with other industries such as food and beverage, and travel, according to figures from the Advertising Standards Authority of Singapore (Asas).
Last year, 25 per cent of complaints received by Asas were against beauty ads, which include those by slimming and hair firms.
Misleading ads can persuade consumers into spending thousands on non-medical treatments, such as herbal products, which have little or no scientific backing when it comes to fighting hair loss, according to dermatologists whom The Sunday Times spoke to.
There are only two products registered with the Health Sciences Authority - minoxidil, a topical lotion, and finasteride, an oral medication - that have been proven to work, said Dr Lynn Chiam, a dermatologist at Mount Elizabeth Novena Hospital.
The haircare industry has come under the spotlight recently after it was reported that a 75-year-old woman who went for a $50 promotional treatment last month was pressured into paying a $4,000 deposit on a $15,600 hair package.
Initially, staff at the Funan outlet of Beijing 101 refused to return the money, arguing that her contract was a binding one. But Madam Susan Koo Moi finally got the $4,000 back last Wednesday, through the Consumers Association of Singapore (Case).
Since The Straits Times wrote about her plight two weeks ago, it has received numerous letters from other consumers complaining about similar hard-sell tactics at hair treatment centres while trying out promotional services.
Non-medical establishments, such as Beijing 101, are not regulated with the same rigour as medical practices, according to Dermatological Society of Singapore president Lim Yen Loo.
There is also no good scientific evidence that products such as gingko biloba, ginseng and other herbs work in preventing hair loss or promote hair growth.
"It is not uncommon for dermatologists to see patients after they had gone for multiple expensive sessions at these 'hair centres' without any improvement," she said.
Hair loss could be due to many different reasons, and the treatment should be tailored accordingly, said Dr Chiam. The most common type is male and female pattern hair loss that becomes more apparent with age.
"However, hormonal changes during pregnancy, illness, stress, sudden change in weight, scalp irritation and scalp infection can all give rise to hair loss," she added.
Some cases of hair loss, such as those that may occur after childbirth, can be resolved without treatment, said Dr Lim. But people may be led to believe that it was the treatment at hair centres that helped to improve their condition, she said.
According to Associate Professor Tan Sze Wee, who is Asas chairman, many of the complaints it receives about misleading ads are from consumers who felt the claims were inaccurate.
Under the Singapore Code of Advertising Practice, all ads should be legal, decent, honest and truthful.
To pass muster, ads for hair loss treatments have to carry a clearly visible disclaimer that the claims made are not backed by scientific proof.
Companies which cannot substantiate their claims are asked to revise their ads. The association can also ask media owners, such as Singapore Press Holdings and the Association of Media Owners (Singapore) which sit on the Asas council, to withhold advertising space from those which do not comply.
But some believe Asas, which is a council of Case, should go further. Mr Soh Weng Soon, 55, a hairdresser of more than 30 years, said: "Some of my customers who go to them for treatment are desperate and do not think logically, even though the ads contain the disclaimer. The authorities should simply stop these centres from advertising."