Danes joined Brooke Shields this summer (10) as a celebrity spokesperson for Latisse, a treatment from the makers of anti-ageing facial injections Botox.
Latisse bosses warn skin darkening is a reversible and less common side-effect of using the product.
The actress documented her 16-week journey with the cosmetic in a video diary on the Latisse website, admitting she suffered redness around her eyes for "about a week" at first, but hadn't experienced any side-effects since.
The New York Post followed with a report suggesting the effected skin had permanently turned a shade of purple and yellow.
However, Danes' representative has slammed the allegations.
A statement to the newspaper reads: "Your claims are entirely false. We will pursue legal action if you print anything to the contrary. This story should be killed."
A spokesperson for Latisse confirmed company bosses had no knowledge of Danes' alleged side-effect: "We can only speak to what Claire has shared with us regarding her experience with Latisse, which is that she has been pleased with her results and continues to use the product.
"Claire's team has shared with us that she has not experienced skin hyperpigmentation following use of Latisse."