Just about every store hawks its own credit card.

Retailers try to lure you into applying with instant discounts, gifts and offers of no interest or payments for a year.

It sounds tempting, but store credit cards usually aren't worth it. The immediate gratifications are often wiped out by higher interest rates, deceptive promotions and traps that will make you wish you had paid cash or just used the major credit card already in your wallet.

Here are seven good reasons you should avoid store credit card offers.

Reason 1. Higher interest rates. The immediate in-store savings or gifts used to lure you into applying for a card are usually offset by higher interest rates. Whereas the average rate for a major credit card is about 12%, store cards typically charge interest rates of more than 20% a year. Carry a $2,500 balance, and you'll pay an extra $175 or more a year in finance charges.

Reason 2. The reward programs aren't that great. Points or rebates can only be redeemed at one store, and retailers are constantly boosting the amount you must spend to earn those rewards. With the Best Buy Credit Card, you have to charge $500 to get a $20 reward certificate. With the Nordstrom retail credit card, you'll be enticed with two points for every dollar spent, but you need a whopping 2,000 points for a $20 Nordstrom Note. That means you'll have to spend $1,000 to get a 2% reward.

Reason 3. You're likely to spend more. Research shows that shoppers with store cards spend three times more than other customers.

Cardholders can become more focused on racking up points or rebates than finding the best deal at other stores. Merchants encourage that by watching what you buy, then bombarding you with invitations to "exclusive" events and special offers for "our valued cardholders."

Reason 4. You'll be targeted for deceptive promotions. Retailers ply cardholders with offers to "pay no interest" for a year, or even two years, on major purchases. But these deals almost always carry a big catch. If you don't pay off every cent of the purchase by the deadline, you'll be billed for all of the interest on the entire purchase price all the way back to the purchase date. In one recent example we saw, that rate was a whopping 29.99%.

Reason 5. You don't know what you're signing up for. Impulsively applying for a store card at the cash register or promotional kiosk isn't a great way to make financial decisions. With all the distractions, you'll likely feel rushed and won't see all the fees and terms buried in the fine print.

Reason 6. You can hurt your credit score. Each time you apply for a credit card, your credit score dips about 10 to 15 points. Store cards also come with relatively low credit limits that can be quickly used up. Credit score formulas further penalize borrowers who use more than 50% of their available credit.

Reason 7. Store-branded Visa and MasterCards aren't any better. The big advantage is that you can use these cards virtually anywhere. But they typically come with less generous reward programs and more costly terms than other bank cards, including higher interest rates, lower credit limits and shorter grace periods than other credit cards.

In short, your best bet is to keep your wallet sleek and trim by relying on one or two low-interest or truly rewarding major credit cards.

By Craig Guillot

Interest.com Contributing Editor