On the first date, the guy should have worn yellow. Yellow caution tape.

But Cleveland jewelry designer Susan Scaparotti had no idea. She’d met him online. He was a successful medical professional, had owned five dogs and invited her to his suburban country club for a bite to eat.

“I thought, “Wow, this guy is a dog person.”‘

It was a beautiful day, and they chatted on the patio overlooking the 18th green.

“We started talking,” remembers Scaparotti. “I said, ‘What attracted me to you was you have dogs.’

“And he said, ‘My favorite dog died.’

“I said, ‘Oh, what happened?”‘

Scaparotti remembers that the guy went on to say, rather matter-of-factly, that he’d gone out of town and forgotten a rather small detail.

“He said, ‘I left him tied up outside and he starved to death.”‘

In relationship jargon, that is called a “deal-breaker” – a habit, trait or character flaw that makes a successful relationship impossible. Deal-breakers are to love what a cherry bomb is to a rural mailbox.

Anyone who’s ever dated can rattle off at least a few, from the common (“has a criminal record,” “doesn’t bathe regularly,” “is married”) to the obscure (“voted for Ralph Nader,” “collects Smurfs,” “loves auto racing”).

While some are just superficially high standards of picky singles (“I cannot date someone who watches reality TV”), true deal-breakers are a sign of serious underlying relationship problems, says Bethany Marshall, a Southern California marriage and family therapist and author of the book “Deal Breakers: When to Work on a Relationship and When to Walk Away.”

For example, if your girlfriend is rude to waiters and waitresses, it’s probably a sign that she lacks empathy, kindness or is just plain mean. Deal-breaker.

If a guy chews his dinner with his mouth open, it might be a one-time slip-up, says Marshall, or it might be a sign of something more serious. Perhaps he’s childlike and needy, refusing to take responsibility for his actions and expecting you to be a mommy and take care of him. Deal-breaker.

“It’s a deal breaker if it has deeper layers,” she says.

In many ways, relationships are indeed like deals or business arrangements, says Marshall. They must satisfy the needs of both parties.

Those needs can be as basic as being loved and understood or more complex, like wanting children or support while you open a new business.

“The deal breaker is usually the thing that undermines the arrangement,” she says.

While deal-breakers vary from person to person and relationship to relationship, there are a few universal ones, says Marshall:

• When you are working harder than the other person, always making the calls, setting up the dates, fixing the problems – deal-breaker.

• When you find yourself preoccupied with the future because the present is unbearable (“Things will be great as soon as he gets a job,” “She just needs a vacation and she’ll be in the mood”) – deal-breaker.

• When the other person keeps projecting or casting you in roles (“You were checking out that guy,” “I know you didn’t call me last night because you went to the strip club with your friends”) – deal-breaker.

So how can you tell if your partner’s antics are harmless or a legitimate deal-breaker? Look at yourself, advises Marshall.

“How people make you feel is your No. 1 indicator of what kind of a person they are,” she says. “If you’re on a date and you feel feelings that you’ve never, ever felt before and it makes you feel bad or feel guilty, and no one else makes you feel that way, that’s the No. 1 sign.”

Scaparotti certainly had that feeling. Add “no dog killers” to her list of deal-breakers.

That’s right next to “must have screens on windows.”

“I went out with a guy once who told me that he didn’t have screens on his house,” she remembers. “He said he lets the spider webs be the screens.

“I’m not making this up. It’s rough out there.”

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