Not only that, but the extra inflammation associated with certain phases (hello, bloating and cramps) can also be related to the immune system standing guard. “Inflammation anywhere in the body is a result of an activated immune system,” Dr. Cross adds.

It’s not like your period, or any other stage of your cycle, for that matter, is going to be solely responsible for making you sick by any means (it can’t create a virus, after all), but excess inflammation around PMS, for example, can be considered an immune response. Since self-care for the immune system is a buzzy topic right now, knowing what phases of your menstrual cycle leave you feeling in A-plus health, and which require a bit of an immunity boost, can be helpful in enhancing your overall wellness.

All of your wellness patterns can make a difference.

Many of the body’s rhythms rely on biological cycles called circadian rhythms to function, including your sleep, hunger, hormone release, and yes, your period. That’s one of the reasons why traveling internationally can not only lead to jet lag and eating chips at 9 am in the airport, but also to delays or disruptions in your menstrual cycle. Any interruption to these circadian rhythms, like anxiety-related insomnia, could cause added stress in the body. “Circadian rhythm disturbances can have a negative impact on a person’s immune system,” Dr. Cross says. “Chronic sleep deprivation, for example, can lead to a decreased immune response,” she adds. 

Also, besides that, the natural ebbs and flows (pun intended) of hormones in your cycle—you can find a refresher on these here—can have an effect on the immune system’s response. Here’s how each phase typically stacks up in terms of immune health. 

Menstration can be a stress-filled time for the immune system.

When you’re actually menstruating, your levels of estrogen and progesterone are low, because they’ve already done the work of thickening the uterine lining and signaling for menstruation to start. Those fluctuations in estrogen and progesterone can make a difference in your immune health, Dr. Cross says. A 2012 study published in Autoimmune Reviews suggests that the changes in those hormones can present a struggle for the immune system, especially right before and during menstruation. One factor is the inflammation around that time, especially associated with cramps and bloating, which can make chronic autoimmune symptoms worse—immune cells might be functioning lower, while the immune system is struggling to fight off any kind of bacteria or virus during this time. 

The other piece of the puzzle at this time is stress (along with anxiety, mood swings, and the like), which is in no short supply during your period. Stress hormones can also have an effect on your immune system. “Stress is linked to elevated cortisol levels, which in turn leads to weakened immunity,” Dr. Cross says. 

The follicular phase is a powerful one. 

This is the time of the month when the ovaries are preparing an egg to be released. Along with that, levels of estrogen are ramping up. Those high levels of estrogen could be responsible for a stronger immune response during the follicular phase. “Women are known to have stronger immune responses than males,” Dr. Cross says, which we’ve unfortunately seen echoed in the higher number of COVID-19 cases in men.  Research from 2015 in Frontiers In Immunology supports this idea that estrogen could contribute to immune response. 

Research is still developing, Dr. Cross explains, but estrogen receptors are tied to T-cell function. Yes, that makes those immune cells have a heightened response to outside infections, but may also have that same heightened immune response to the body’s own cells (for that reason, people with high levels of estrogen are more prone to autoimmune disorders). Scientists are still debating if estrogen is ultimately strengthening or weakening to the immune system.

Ovulation makes the immune system more lax. 

After the peak of ovulation, the ovaries release an egg, in preparation for potential pregnancy, and estrogen levels dip back down. And during that period of ovulation, 2012 research from the Journal of Leukocyte Biology suggests, the immune system’s function takes a dip to potentially accommodate outside cells (a.k.a. sperm) into the body. 

Ovulation could make the body more susceptible to infection because of that adaptation of the lowered immune response to prepare for a potential pregnancy. The research was done on animals (in the study, mice were more prone to yeast infections during ovulation), but scientists think it could transfer over to humans: People who menstruate could be more likely to catch certain infections in the middle of their cycle. 

The luteal phase is prepping the body for the stress of menstrating. 

During this phase, progesterone is rising, and eventually peaks, in order to give the body the all-clear to menstruate if a pregnancy doesn’t occur. With the rise of progesterone, the immune system’s power may unfortunately fall. “Elevated levels of progesterone are thought to be responsible for the weakened immune response that is observed, rather than estrogen,” Dr. Cross says. And a 2017 Mucosal Immunology study supports that progesterone can lower the ability to fight infections that can affect reproductive, gastrointestinal, and respiratory tracts. 

There’s another component to the luteal phase, as the body nears the PMS stage of the cycle. Toward the end of the luteal phase, cortisol levels are heightened, Dr. Cross explains, which is likely going to make the immune system work harder to stay healthy.

Tracking your cycle along with your immunity. 

It’s always smart to closely track your cycle, and observe which times of the month leaving you feeling like you naturally need a boost. That way, you’ll know when you need to make extra healthy choices, such as more supplements, more antioxidant-filled fruits and vegetables, and more stress-releasing exercise and mindfulness activities to make sure you’re feeling your best.