At a Professional Presence workshop, we tackled the sometimes-sticky issue of appropriate attire for the office. “Why shouldn’t I wear jeans and a t-shirt?” they wanted to know. “We’re business casual!”

My answer: When you get dressed for work, the big issue isn’t what can you get away with today. You’d be better off to think instead about how you want to be perceived.

Wear professional clothing and people think of you as (surprise!) a professional. Show up for work looking like you’re running errands on a Saturday morning, and they draw a completely different conclusion.

As if wardrobe weren’t enough of a minefield, for women there’s another aspect of appearance to consider.

How important is it to be attractive?

It’s well-documented that physically attractive people—men and women both—are rewarded in business. Just for starters, they make more money than the rest of us. Over the course of a career, it can be a lot more.

But being attractive is actually a double-edged sword for women. It’s one thing when they’re applying for low-level positions. But when they move into managerial or executive roles, it turns out pretty women are often seen as less qualified.

They call it the “beauty is beastly effect.”

This is why the young CEO of a Silicon Valley start-up dyed her blonde hair brown and ditched her contacts for glasses when she was looking for investors. A woman in venture capital told Eileen Carey she’d be taken more seriously as a brunette.

Carey told BBC News “For me to be successful in this space, I’d like to draw as little attention as possible, especially in any sort of sexual way.”

So, Carey got rid of a look that made it more likely she would be flirted with. She wears loose-fitting “androgynous” clothes to work. Carey wants to be seen as a business leader, not a sexual object. And that choice has worked out well for her.

Gender researchers have examined “Beauty is Beastly” in some detail.

At the University of Chicago, sociologist Jaclyn Wong concluded there are really two aspects to attractiveness. We’re born with things like a symmetrical face or being tall. We work on other things: make-up, hairstyle, wardrobe.

It’s those fruits of our effort that make the biggest difference for women. Wong says there can actually be an early-career advantage to looking like you just emerged from the pages of Vogue or Cosmo.

Attractiveness is an asset, it appears … until a woman moves up the ladder.

In senior positions, The Look becomes a liability. Beauty and brains don’t seem to go together in conventional wisdom. Our stereotypes say looking lovely—and the effort it entails—are incompatible with being competent and capable.

So, what’s a woman to do?

If I want to succeed in business, do I have to show up at work every day with a naked face, un-styled hair, and clothes made for comfort instead of fashion?

If that’s your look, bless you. Me, I vote for putting some effort into appearance, no matter what the researchers say.

(And I notice that the more, um, seasoned I get, the more effort it takes. I’m not alone in that, am I?)

A good rule of thumb comes from an image consultant with a background in Human Resources. Sylvie di Giusto says if your appearance is a topic of conversation among colleagues or clients, that’s an argument for a make-over, right there.

She told CNN whether you’re perceived as too attractive or not attractive enough … the problem is with people talking about how you look or what you wear instead of about your brilliant work. That’s a distraction you don’t need.

What’s even more important than an appealing appearance?

Whatever you’re wearing. However your hair looks. Whether you’re plain-faced or made-up to the max. If you radiate confidence, you win.

Confidence creates a strong first impression. And as people get to know us, they’re more likely to trust us, buy from us, follow our lead if they perceive us as confident. Not cocky, not arrogant, but self-assured about who we are and what we can do.

If that’s an issue for you, focus on developing your confidence, no matter what you see when you look in the mirror.

And please weigh in with your experience. How has physical appearance had an impact on your career?

Share your story in the comments below.