Why do I feel sick before my period?

Q: Does a woman’s immune system weaken at certain times of her menstrual cycle? I have always noticed that if I get sick, it’s almost always just before I get my period.

Experts say that while there isn’t enough data to prove that you’re more likely to feel sick before or during your period, there are some hints that it is possible. Emerging research suggests that the immune system can fluctuate during this time, sometimes exacerbating underlying chronic disease symptoms or creating new ones that some women may mistake as signs of a new illness.

Just before a period, for instance, some women report symptoms typically associated with the flu, like body aches, malaise and even fever. This so-called period flu isn’t caused by an actual pathogen, said Dr Taraneh Shirazian, a gynaecologist at NYU Langone Health. But it can be the result of a person’s immune response to natural inflammation as the uterus cramps and sheds cells. “It’s how your body perceives the inflammation,” she said.

Hormones may also be to blame for these symptoms, Dr Shirazian said. Luteinizing hormone, or LH, surges just before ovulation and then sharply drops when a period starts, she said. As LH levels shift, people can experience fatigue, bloating, headaches and nausea. “Some women go through this with really aggressive symptoms every cycle, every month,” Dr Shirazian said.

In a 2018 review in partnership with the period-tracking app Clue, researchers also noted that in women with certain underlying illnesses — like inflammatory bowel diseases, epilepsy and autoimmune disorders — symptoms associated with the illnesses sometimes worsened during ovulation, improved about a week later and worsened again during menstruation.

This, said Sabra Klein, a microbiologist at the Johns Hopkins Bloomberg School of Public Health, could be the result of seesawing hormones and immune system changes over the course of a period.

Other research has found that between 19 and 40 percent of women with asthma have reported more intense and frequent asthma flare-ups or attacks right before or during their periods. Perimenstrual asthma, as it’s called, has been linked to increases in asthma-related emergency department visits and hospitalizations, including intubations.

Some small studies have also shown that women with multiple sclerosis reported worsening symptoms right before or during their periods. And patients with lupus have reported more pain and fatigue around their menstrual cycles.

The evolutionary function of the menstrual cycle is to give women an opportunity to become pregnant, said Dr Kimberly Keefe Smith, a ​reproductive endocrinologist and gynaecologist at Brigham and Women’s Hospital in Boston. When fertilisation does occur, some parts of the immune system are suppressed so that the body does not reject the foetus.

During the menstrual cycle, the ovaries secrete oestrogen and progesterone, which affect different branches of the immune system in different ways depending on the part of the body. Progesterone, in particular, can be an immunosuppressant when present at high levels in the body, like during pregnancy, Dr Keefe Smith said. But oestrogen and progesterone alone can’t explain a weakened immune system, she added; patients who receive extra doses of the hormones during certain medical treatments or while on birth control, for example, are not more susceptible to feeling sick.

Without definitive data, scientists can’t provide clear guidance on how women should think about their chances of feeling sick based on their cycles.

“This has been grossly understudied,” Dr Klein said. “I can’t really tell you if you’re more likely to get a cold or have infections, because the more detailed studies just haven’t been done.”

While additional research is needed to better understand how the menstrual cycle influences disease susceptibility, she added that if you consistently find yourself feeling sick at a certain point in your cycle, don’t ignore it. You can take steps to protect your health leading up to your period: Make sure you’re eating a balanced diet, getting enough sleep and washing your hands for at least 20 seconds. “Every woman knows their body best,” Dr Klein said.

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