If you find a great online deal for high-end makeup that seems too good to be true, go ahead and assume it is. Or, just keep in mind that the money you’re saving is due to the fact that rat droppings might very well be in that makeup. Though this article focuses on the UK’s problem with counterfeit makeup, the problem can be found anywhere there’s Internet. On eBay, for example, there are posts for how to spot counterfeit products, particularly for MAC. Two things to watch out for: the packaging (though the differences can be subtle) and ridiculously good bargains. If you’ve experienced an allergic reaction to makeup, it could be an indication that the product contains excess preservatives or other low-quality ingredients. And, in some cases, arsenic and cyanide have even turned up in some counterfeit products, though—rest assured—rat droppings are a much more likely possibility, says authorities. Have you ever been duped by counterfeit makeup? Or do you know any tricks for how to spot it? Tell us in the comments!