WASHINGTON — The Food and Drug Administration is warning cosmetics maker L’Oreal SA that its website for Genefique exaggerates the benefits of the skin cream, portraying it as a drug with medical properties.

The agency issued a warning letter Friday to the company’s Lancome unit, which markets Genefique Youth Activating Concentrate and similar antiwrinkle cosmetics. The letter was posted to the FDA’s website Tuesday.

Lancome claims Genefique ‘‘boosts the activity of genes’’ and contains special ingredients that ‘‘stimulate cell regeneration to reconstruct skin to a denser quality.’’

The agency says only drug products are allowed to make such claims, and Lancome has not submitted necessary data to market its product as a drug.

The letter instructs the company to respond to regulators in 15 business days with a plan for correcting the language.