Claims that products are "dermatologically tested" are confusing and potentially misleading, say researchers.
Health Which? is calling for more information on cosmetic tests
Health Which? says the wording, found on many cosmetics, toiletries and washing powders, wrongly implies certain agreed standards have been met.
A survey found consumers gave several different explanations for the term.
Health Which? says its findings show there need to be industry-wide definitions for what the claims mean.
It says there is an implication that "dermatologically tested" or "dermatologist approved" means the product has reached a certain level of safety or effectiveness.
But each company has its own procedure for testing a product and deciding what results need to be achieved.
Health Which? says this means consumers have no way of comparing claims.
The magazine says the tests may not even replicate how a product is actually used, and the labelling does not explain what the tests were designed to show, or whether the product passed those tests.
'Lack of openness'
In its survey of 1,000 consumers, the magazine found a quarter interpreted the claims literally to mean the product had been tested on human skin.
Thirteen per cent of those questioned believed "dermatologically tested" meant the product was kind to skin, 22% thought it would not cause allergies and 10% thought the product was unlikely to cause skin allergies.
But many of those questioned said they did not know what the term meant.
Health Which? contacted 10 cosmetics companies to find out what tests they carried out and what evidence they had to support their claims.
Accantia, Beiersdorf, The Body Shop, Boots, Johnson & Johnson, Level Faberge, L'Oreal and Procter and Gamble submitted general information about their testing procedure.
But Health Which? said they did not provide enough information for independent experts to assess the claims.
Health Which? said the companies' lack of openness meant consumers could not judge the extent and quality of these tests which support the "dermatologically tested" claims.
Sue Freeman, acting editor of the magazine, said: "The research shows that a 'dermatologically tested' claim on one product may mean something completely different to the same claim on another product.
"This is confusing and potentially misleading. Without standard definitions, and with companies refusing to supply details of their tests and results, these claims are meaningless, and consumers are left guessing about the benefits implied by such claims.
"We want to see more openness from companies, and standard definitions for derma claims."
A spokesman for Revlon, which makes the Almay brand for sensitive skins, told BBC News Online: "We regret that we were unable to respond by the deadline for response that HealthWhich? imposed.
"However, dermatologists are involved in every aspect of Almay safety testing including patch test analysis, allergy and use testing as well as final formula review."