ABC News' Becky Worley reports:

Looking for an online deal on brand name makeup? Be careful: the world of knockoffs isn't just about purses; makeup that claims to be something it's really not can be found all over the Internet.

Paying 25 dollars for face powder or mascara hurts, but buying a knockoff could hurt more. I ordered brand name mascara, foundation, lipstick, and pore minimizer from third-party vendors off of eBay, Amazon and some online makeup "outlets" to see if any might be knockoffs.

A few observations about buying discount makeup online:

1) I noticed that the discount items I ordered weren't that much cheaper. For example the Benefit Mascara was about $6 less than the retail cost

2) The sellers I purchased from on eBay all had multiple lots of items; they seemed like businesses, not individuals.

3) On Amazon, all the items sold at a discount were from third-party sellers.

4) At supposed "outlet" stores, the items were much much cheaper than retail, but the shipping was a flat rate of $40.

As the products started rolling in, the first package arrived from China. The waybill on my MAC makeup package showed the originating city as Beijing. When I opened it up, the foundation and lipstick looked like authentic products, but when I compared them to the same items I'd purchased in the MAC store, there were obvious defects and graphics differences on the packaging. The mirror on the compact was chipped and the overall weight of the foundation seemed less.

Of all nine products I ordered online at Amazon and eBay, four seemed suspicious or certainly different in graphics and looks from the authentic products: the Benefit mascara & pore minimizer and MAC foundation and lipstick.

We sent the Benefit mascara and the MAC foundation to the labs of the nonprofit health group NSF International to be tested. NSF found the Benefit Mascara was not comparable to the one purchased at an authorized retailer- the packaging and chemical formulations weren't the same. NSF said the chemical differences were just slight and not of concern .

The more staggering result was the MAC foundation we bought from a third party vendor outlet site. NSF said it contained 260 micrograms of lead per gram compared to the authentic version's 0.27 micrograms per gram- that's nearly 1,000 times as much!

Dermatologist Dr. Gloria Graf says depending on the contents of these knockoff makeup products, there is a risk "they can permanently scar you if you get a reaction on your skin that is severe enough".

So how do you spot a knockoff online?

*The prices on brand-name makeup products are highly regulated by the manufacturer. If the deal is too good to be true, there's probably something wrong.

*If you aren't sure about a product, search "how to spot a fake (name of the product)." A cadre of beauty bloggers have posted very helpful write-ups and pictures detailing the graphics mistakes and discrepancies that they say indicate you may have a knockoff.

*Don't depend on the picture online to tell you if it's a knockoff. It's possible that you will see photos of the real product online, but what arrives at your doorstep could end up a graphically different knockoff.

*If a website doesn't accept a credit card on their own site with an HTTPS or if they use a third party payment service (if it redirects you to a different website to take your credit card), be wary. It may mean previous purchasers contested their charges with the credit companies and those vendors have been black-listed.

*Knockoffs purchased online are often sold in big lots. Those can in turn be sold at flea markets or mall kiosks. The knockoffs could be out in the physical world too.

*If the product's consistency or texture just doesn't feel or look like the authentic brand, don't use it.

*Both eBay and Amazon told us they work hard to prevent the sale of knockoff goods on their sites, and investigate any user reports of them and take appropriate actions. eBay even told us they "restricted the account in question" after we reported our experience to them.

*MAC and Benefit told us that the only way to ensure the quality of their products is to buy them from an authorized retailer.