Using a credit or debit card on vacation abroad can be an expensive proposition regardless of the strength of the dollar. Most cards charge a fee of around 3% for foreign transactions. What some consumers may not know is that this fee applies even when the transaction is made entirely in dollars and regardless of whether the consumer has actually left the country.

Historically, banks charged consumers traveling abroad for the service of currency conversion. A traveler who used a credit card to pay for dinner in a Parisian bistro, for example, would have gotten a bill in francs or euros at the table, and later seen the charge show up in dollars on a credit-card statement. Visa (V) or MasterCard (MA) would have done the currency conversion when processing the transaction, and charged the card-issuing bank a 1% fee for the service. That bank would then pass the fee onto the customer plus another 1% or 2% markup, for a total fee of 2% or 3%.

A few years ago, a new back-end service made it possible for businesses that serve an international clientele to offer on-the-spot currency conversion, so that American in Paris could get the check for dinner in dollars, says David Robertson, the owner of the Nilson Report, which tracks credit-card industry trends. Payment networks and card issuers then replaced currency conversion fees with cross-border or foreign transaction fees, Robertson says, to avoid losing revenue because they were doing less currency conversion.

Now, a looser definition of foreign transactions means that more transactions incur these fees, including online purchases made from a consumer s home in America and paid for in dollars. That net has been spread much more broadly now, says Ben Woolsey, a spokesman for CreditCards.com.

In its most fiscal second-quarter earnings report, Visa told shareholders that international transaction revenues had grown 22% over the previous year due to an increased volume of transactions. MasterCard also reported a 10.9% increase in cross-border transaction volume in the first quarter, and a 39% increase in cross-border transaction fees. That growth likely stems from a combination of more transactions being considered cross-border and a growth in the actual number of transactions, Woolsey says. Some credit-card issuers have also hiked the percentage fee they charge in the past year or so, he says.

Transaction fees like this are on the rise now, even as penalties like late fees or overlimit fees are under new restrictions, says Ardie Hollifield, a senior research associate with the Pew Safe Credit Cards Project and a co-author of the project s most recent report on the state of the credit-card market. Cash advance, balance transfer and annual fees all rose between the project s October and July reports, Hollifield says.

Banks aren t charging these foreign transaction fees without cause, industry analysts say. There are costs involved in running a global payment network, Robertson says. In particular, following up on fraud is more complicated when overseas merchants are involved, and as phishing schemes and other online frauds become more common, banks need some way to recoup those costs, Woolsey says.

It s important for consumers to know that you can make a cross-border transaction sitting in your own living room, Robertson says. One thing consumers can watch for is a seemingly convenient offer to process a transaction in dollars. For merchants, showing prices in a shopper s home currency makes them more comfortable and more likely to buy, Robertson says. But whether shopping in Nice or Nebraska, if a merchant does currency conversion, they ll charge a fee for that service and that ll be on top of the foreign transaction fee a credit card will charge. American shoppers should decline on-the-spot price conversion to avoid paying two service charges on the same transaction, Robertson says.

Americans shopping online should pay attention to where the retailer or seller is based and where the product will be shipped from, Woolsey says. Third-party sellers found on Amazon (AMZN) or eBay (EBAY) could easily be using foreign banks, which would mean paying a foreign transaction fee, he says. People shopping for a foreign-made product could consider buying from a U.S.-based retailer rather than direct from the overseas company, says Schwark Satyavolu, the CEO of BillShrink.com. If you re looking at a company that s foreign, then it is likely they re using a foreign bank account, although not necessarily and there s no way for you to tell, Satyavolu says.

Buying a plane ticket from a foreign airline could also incur a cross-border transaction fee. In some cases, even going through a third-party travel booking site like Expedia (EXPE) or Orbitz (OWW) might not avoid the fee, because the way the transactions are conducted varies from flight to flight, Satyavolu. Using a U.S.-based site would at least reduce the odds of paying a foreign transaction fee, he says.

Capital One (COF) doesn t charge foreign transaction fees, and doesn t pass on payment network fees to its customers, Woolsey says. Their core demographic is a less-upscale consumer who likely doesn t travel much, Robertson says.

Fee-hating consumers can also consider a credit union card, Hollifield says. While 91% of bank cards charge foreign transaction fees, only 57% of credit union cards do, and the median fee charged by credit unions is slightly lower, according to the most recent Safe Credit Cards Project report. That trend holds true for other types of fees, like balance transfer or cash advance fees, as well, Hollifield says.