It turns out that pivotal moment when a couple settles into everyday love (when sexy, witty, and pretty take a backseat to easy, cozy, and lazy) is when they’re most likely to emerge.

Cunningham describes this phase as being a transition from “front stage behavior”—when we’re always on, trying to make an impression—to “back stage behavior,” when we drop all pretense and share our “true” selves.

Sometimes, all too true: After a year or two, he says, we tend to act freely—and that begets trouble. While an allergen may start as a mere irritation, over time it becomes “symbolic of larger things,” says Cunningham.

Consider, for example, smelly feet guy: Each night he takes off his socks before bed, leaving them on the floor, where the odor wafts up to his partner.

“She’s disgusted. She wants them in the hamper,” Cunningham says. “He’s tired. He wants to go to sleep.”The real danger, he says, is that “neither of [them] see the ‘sock issue’ as jeopardizing the relationship.”

Yet this is when a couple first flirts with disaster: She complains; he dismisses her reaction as irrational and moody. The more he dismisses, the more she sees him as selfish and uncaring. Suddenly, stinky socks are grounds for couples therapy.

“You do a slow burn,” says Robin M. Kowalski, psychology professor at Clemson University. “Anger accumulates over time and you wonder, ‘Why doesn’t he have more respect for me?’” What may have seemed cure and innocent during the first few months of dating starts to grate, until a tic is interpreted as a personal affront—and battle lines are drawn.

The Rx for Allergens
While, as of yet, there’s no Social Al-Anon, many relationships do survive these annoyances, Cunningham says, because the perks of intimacy outweigh the quirks. Still, learning to cope requires effort and finesse.

When confronting an allergen, the first step, says Kowalski, is early, clear communication. A friendly intervention, if you will. “Tell the other person how you’ve been feeling, without being accusatory, and see how they respond.” Do it early enough, and your partner may be able to curb the behavior before a bonafide allergy evolves.

But the way you communicate your request for change is key, Cunningham adds. A sock in the hamper should be rewarded, yet a stray on the floor shouldn’t elicit an angry response. If you explode or act cold and aloof, he’ll have no incentive to change.And worse, that sock becomes a fight tripwire.

Women, especially, should take note: Kowalski found these habits may be bigger dealbreakers for us than for men because we’re more sensitive to social allergens...and more likely to be physically turned off by them, too.

But what if a mate just can’t change? You have two choices, says Cunningham: “Honey, you left the cap off again.