Pet owners shopping for Frontline, Advantage and other flea control products for their pets should be on the lookout for counterfeit versions of those products appearing on retailers' shelves. According to the U.S. Environmental Protection Agency, these products are packaged in cartons designed to look like legitimate versions of Advantage and Frontline but are not approved by the EPA.

These counterfeit products may be missing instruction leaflets required by U.S. law. The packages also may not feature required child-resistant packaging and the applicators may not be the appropriate size dosage for the animal indicated on the package. Using such products could put your pet at risk as the counterfeit products may contain too much or too little dosage or different ingredients all together, according to the EPA. The packages for the legitimate and counterfeit versions of each product look similar, so you must open the packages and examine the contents inside to determine legitimacy.

Legitimate Frontline products will meet the following criteria:

• The lot number on the carton and the lot number on the applicator package or individual applicators will match.

• The instruction leaflet is included and provides safety information, U.S. telephone numbers and storage and disposal instructions.

• The applicator package is child resistant, and directions for opening the applicator package include an illustration that looks like the applicator package.

• The applicator package has a notch between each individual applicator package. Text on the package is in English only.

• Each individual applicator has a label that includes the name of the manufacturer (Merial); the EPA registration number; the contents measured in fluid ounces (not metric measurement); a list of active ingredients, and the statements "Caution", "Keep out of reach of children" and "See full label for additional directions" in English.

• The applicator label for dog products includes the size of the dog in pounds.

For Advantage products, the following criteria can be used to determine legitimacy:

• All applicator tubes will feature directions printed in English. Any applicator with instructions in another language is counterfeit.

• Applicator tubes will include the EPA registration number, word "WARNING" and a child-safety statement.

• Also on the tube is a reference to referring to the main label of the product for directions, as well as the name of the manufacturer (Bayer).

• Legitimate products will feature an active ingredient statement that matches the statement on the retail carton. Counterfeit products may feature different statements.

It is important to note that the EPA also considers versions of the drug sold in foreign countries - but imported into the United States - to be counterfeit as well. Products purchased in foreign countries may not have the same safety warnings or child-resistant packaging as products approved for sale in America and the dosages and ingredients may be different. If you have purchased counterfeit products, the EPA recommends you dispose of the product according to local solid waste guidelines. You should also notify the staff of the retail outlet you purchased the product from as well as the EPA regional office in your state.

Click here for more information about these counterfeit products.