HACKENSACK, N.J. — Moisturizers may speed skin cancer in reformed sunbathers, even years after giving up on tanning, according to a Rutgers University study of mice.

Four different brands of moisturizing creams caused tumors to form faster and larger in hairless mice that had been pre-treated with ultraviolet radiation, the Rutgers researchers reported Thursday in the Journal of Investigative Dermatology.

“We don’t know what happens in humans,’’ said Alan Conney, who headed the study. “But this is a red light saying there should be some epidemiological study in human populations.’’

Manufacturers of the products — Eucerin Original Moisturizing Creme, Vanicream, Dermabase and Dermovan, all chosen randomly for the study — refuted the findings Thursday.

“Eucerin Original Creme has been on the market for more than 100 years and is a highly respected, dermatologist-recommended brand,’’ a statement by Beiersdorf Inc. said.

“It has been widely used by both individuals with normal skin and those with diseased skin under the care of physicians without any incidents of this nature ever reported.’’

PSI Pharmaceutical Specialties, makers of Vanicream, said the results had “doubtful significance,’’ given the methods that were used.

“Vanicream Skin Cream has been safely recommended and used for nearly 30 years,’’ the company said in a statement. There was “no statistical difference’’ in the number of mice that developed tumors whether treated with Vanicream, water, or not at all, it said.

A spokesman for Healthpoint Products said Dermovan is not a moisturizer, but is a base sold to dermatologists to formulate other products. He questioned why it was even in the study.

“Dermovan is a very small product, so small I didn’t know we provided it anymore,’’ said Mark Mitchell, the spokesman. “It’s been around probably 50 years and there’s never been an issue with the safety of the product.’’

Paddock Laboratories, Inc., which manufactures Dermabase, did not answer requests for comment.

Conney said it is not known which ingredients act as the mechanism that could promote skin cancer. “There was no common ingredient’’ in the moisturizers that was suspect, he said. “It has to involve the combination of ingredients.’’

Pre-treating the mice with ultra-violet rays put them at “high risk’’ for skin cancer, Conney said.

Although mice have much thinner and more permeable skin than humans, Conney said the study “is similar to humans who may be exposed early in life to a lot of sunlight, then not as much later in life, but still come down with skin cancers.’’

The Rutgers study focused on nonmelanoma cancers in squamous and basal cells, which are located in the outer and inner layers of the skin, respectively.