Bloating, mood swings, fatigue. Sometimes you just know when your period is about to make its way back into your life. There are so many different symptoms attributed to premenstrual syndrome, or PMS, ranging from only slightly annoying to downright debilitating every month (or so). One you might not have considered? Your immune system is weaker on your period.

That’s right, you might be more prone to getting a case of the sniffles—or at least feeling sick—during your flow.

“Hormones take on a roller coaster ride during the menstrual cycle, and these fluctuations impact the immune system in many ways,” says Ashanda Saint Jean, MD, associate professor of obstetrics and gynecology at New York Medical College in Valhalla, New York.

What does this actually mean for your health each month? Find out here, plus how to keep your immunity up while on your period.

The connection between your period and your immune system

Shifts in the hormones estrogen and progesterone that happen during your menstrual cycle can affect your immune system function. Progesterone, in particular, has immunosuppressive properties that may make it harder for the body to fight off infection, according to a March 2023 review in the Archives of Gynecology and Obstetrics¹.

This means, when your body’s levels of progesterone surge after ovulation (to help prep your uterus for a fertilized egg), you may be more susceptible to getting sick, says Dr. Saint Jean. The authors of the Archives of Gynecology and Obstetrics review actually described it as a “window of opportunity” for possible infection. Who knew?

There’s more: Spikes in estrogen (which happen right before ovulation) lead to an increase in the production of histamine—the immune system chemical that sets off allergic reactions, per the National Library of Medicine. “Symptoms from an increase in histamine mimic that of an allergic reaction or brief flu-like illness. Those symptoms may include nausea, dizziness, generalized malaise, and overall fatigue,” Dr. Saint Jean says. This is akin to a “period flu” that many people describe having during their flow.

Hormonal shifts may even trigger inflammatory changes that can affect chronic conditions, Dr. Saint Jean says. For example, up to 40 percent of women with asthma get worse symptoms before their periods, per an August 2016 review in Multidisciplinary Respiratory Medicine². And while more studies need to be done to determine this connection, some period-related hormone changes are thought to play a role in exacerbating other conditions like diabetes, arrhythmias, and even schizophrenia, according to an older May 2012 review in Autoimmunity Reviews³.

Ultimately, not everyone is bound to get sick during their menstrual cycle; some people have stronger immune systems than others. But if you keep getting sick each time you’re about to get your period, let your doctor know. They can help you get to the bottom of things.

“Encouraging our patients to be proactive about their health can be a game-changer for many.”—Ashanda Saint Jean, MD, OB/GYN

How to stay healthy during “that time of the month”

Doubling down on the self-care basics can generally help you feel your best throughout your cycle and might make you less likely to get sick. “Encouraging our patients to be proactive about their health can be a game-changer for many,” Dr. Saint Jean says. You can:

1. Choose wholesome foods

Keeping consistent with a balanced, nutrient-filled diet is your first line of defense here, says Dr. Saint Jean. Try incorporating anti-inflammatory foods—which can help strengthen your immune system—like green leafy veggies, nuts and seeds, fatty fish, and berries, per Harvard Health Publishing. A September 2020 systematic review in the International Journal of Preventative Medicine⁴ also found that eating more calcium was associated with a reduction in PMS symptoms like anxiety and water retention.

Dr. Saint Jean also recommends keeping sugary, refined, and ultra-processed foods to a minimum.

2. Get enough sleep

Good quality sleep is a must for keeping your immune system firing on all cylinders, especially before your period. Getting enough shut-eye may also help relieve a variety of PMS symptoms, including anxiety and mood swings, per the Mayo Clinic. “Ideally, get at least 8 hours of sleep,” Dr. Saint Jean recommends. If you’re having trouble falling asleep, doing a meditation or some light stretching may help you relax.

3. Find feel-good ways to stay moving

Exercise reduces PMS symptoms as a whole, which can include those flu-like symptoms, per a January 2020 systematic review in Complementary Therapies in Medicine. You’ll reap the biggest benefits if you exercise at least 30 minutes a day for most days of the week, per the Mayo Clinic. That said, if your energy levels aren’t at their peak, stick with gentle workouts like yoga, walking, or Pilates. Hormone shifts during PMS can make strenuous exercise feel harder (i.e., harder to cool off or have enough stamina). This is totally normal; just take it at your own pace.

4. Do something for your stress

Turns out, stress can weaken your immune system and cause you to get sick more easily, per the Mayo Clinic. It can also exacerbate the emotional swings you might be dealing with before and during your period. To help relieve stress, Dr. Saint Jean is a big fan of meditating or booking a massage, but find what works best for you. This could include anything that de-stresses you, like journaling, catching up with friends, or engaging in a new hobby.

5. Talk with your doctor

If your period symptoms (including the “period flu”) are affecting your quality of life, it might be time to reach out to a trusted doctor. They can recommend treatment options like certain lifestyle changes, supplements, or hormonal birth control to help stabilize your hormones and reduce period symptoms, per Johns Hopkins Medicine.

When to see a doctor

If you are frequently getting colds or other illnesses before or during your period, let your doctor know. They can help determine whether it’s a symptom of PMS or another underlying condition. Similarly, if your periods come with extreme abdominal or pelvic pain, heavy bleeding, and emotional or mental health challenges, speak with your doctor about potential PMS treatments. While PMS is common, it doesn’t have to take over your life every month.

FAQ

Can being sick affect your period?

Yep, it can. A bad infection like the flu or a stomach bug can definitely delay your period or even make you miss one altogether, per the National Institutes of Health. One missed period likely isn’t cause for concern, but let your doctor know if you notice cycle irregularities are becoming a regular thing. (You may also want to take a home pregnancy test, if there’s any chance you could be pregnant.)

Why do I keep getting sick every month?

The average adult gets two or three colds per year, according to UpToDate.com, so getting sick every month definitely isn’t par for the course. Thing is, there are tons of factors that can affect your immune function, including stress, lack of sleep, an underlying health condition, or frequent exposure to germs that cause viruses and other illnesses. To figure out what might be going on, the best move is to start by talking with your doctor. They can run blood tests and other exams to get to the root of the problem.

What is “period flu?”

“Period flu” is basically a term to describe flu-like symptoms (think: body aches, fatigue, headache, fever, and GI issues) that some people get before their period. It stems from a shift in hormones estrogen and progesterone, so you don’t actually have an infection, but it can feel like you’re sick, according to UW Medicine.

—reviewed by Andrea Braden, MD, OB/GYN