The acne period

Modern science has finally caught up with what women have been saying for ages: Acne rises and falls with the menstrual cycle.

A new study found that the skin breakouts can follow the same or a similar 28-day cycle as the menstrual period, flaring just before bleeding starts, and calming down soon after bleeding begins.

"It's one of those facts of medicine that everybody kind of took for granted as being true, but no one really bothered to see if it held up to scientific scrutiny," says Dr Ted Daly, director of paediatric dermatology at Nassau University Medical Centre in New York. The fact that it did is what gives this research impact, says Daly, who was not affiliated with the study.

What is acne?

Acne is an inflammatory condition of the oil-producing glands and the hair follicles. If anything blocks or hampers the flow of oil from the tiny pores leading from those glands to the skin's surface, it can lead to acne. Likewise, anything that increases oil production can also encourage pimple formation - including hormonal activity - and therein may lay the link to the menstrual cycle.

"The hormones may modulate sebaceous activity of inflammation," says Dr Guy Webster, study co-author and professor of dermatology at Thomas Jefferson Medical College in Philadelphia.

He does warn, however, that hormones alone are not the sole reason for acne, and women should not be quick to blame their breakouts only on their menstrual cycle.

"Acne is the combination of bacterial growth, inflammation, plugging and hormones," says Webster.

The size of pores

One little-known factor that can sometimes figure into the equation is the size of a woman's pores. Indeed, the smaller the pores, the greater the chance of clogging, which is the first step of pimple formation. Perhaps not coincidentally, the researchers note that pores also shrink and expand in direct relation to the menstrual cycle - with pores smallest on days 15 to 20.

As Daly points out, this just happens to be the same time when hormone activity is the highest - just following ovulation around mid-cycle. Since pimples take about a week to form, he says, the hormone peak is likely to make the breakout period be just prior to the start of bleeding.

Webster agrees. "The timing of hormone change with acne flares may not be instantaneous; there could be a several day [or] week lag in disease response," he says.

Listen to the researchers

Research studies showed that 53 percent of women over age 33 had among the highest rates of premenstrual acne, higher than women under age 20, who reported only a 39 percent increase in acne right before the onset of their period.