Do you often get UTIs during your period? It's not a coincidence. There are several explanations for this inconvenient timing, and it's worth understanding what's happening in your body at that time.

During the menstrual cycle, hormone levels fluctuate significantly. Just before and during menstruation, estrogen levels drop considerably. However, these hormones don't just regulate your cycle: they also play a protective role for your vaginal and urethral mucous membranes by maintaining a healthy environment and strengthening their resistance to bacteria.

That's why, when estrogen decreases, this natural protection weakens. Tissues become more fragile and less effective at preventing bacteria from settling in. This is why some women develop cystitis as early as the premenstrual phase, even before bleeding begins.

Normally, your vagina maintains an acidic pH (between 3.8 and 4.5) which prevents the proliferation of pathogenic bacteria. It is lactobacilli, the "good" bacteria in your vaginal flora, that maintain this protective balance.

During menstruation, menstrual blood has a more basic pH (around 7), which alters this environment. Lactobacilli struggle to maintain their role, and the bacteria responsible for urinary tract infections, especially Escherichia coli, then find favorable conditions to multiply and move up towards the bladder.

Naturally strengthening your vaginal microbiota by repopulating it with good bacteria, i.e., Lactobacilli naturally present in your intimate flora, is a good solution to prevent this imbalance and recurrent cystitis.

It's less well known, but the immune system also experiences fluctuations during the cycle. During the menstrual period, your immune defenses are slightly weakened. This decrease is explained by hormonal changes, but also by fatigue, stress, or pain that often accompany periods.

Your body mobilizes a lot of energy for the menstrual process, which temporarily makes it less reactive to infections. You may have noticed that other minor ailments (like pimples) also occur at this specific time in your cycle.

Unlike men, female anatomy naturally makes women more vulnerable to urinary tract infections because the tube that evacuates urine (the urethra) is only 3 to 4 centimeters long and is located very close to the vagina and anus.

And since menstrual flow creates a humid environment that favors the movement of bacteria between these different areas, intestinal or vaginal bacteria only have a short distance to travel to reach the urethra, then the bladder. This proximity, already problematic under normal circumstances, becomes even more delicate with humidity and menstrual discharge.

Another reason to consider is sanitary products. Indeed, pads create a warm and humid environment favorable to bacterial multiplication, especially if they are not changed regularly. As for tampons and menstrual cups, they can put pressure on the urethra or irritate mucous membranes if they are poorly positioned or kept in for too long.

The worst part… Some products contain perfumes, dyes, or synthetic materials, often responsible for local irritation. Sensitivity varies from woman to woman: what suits one perfectly may irritate another. It is important to find the products that suit you.

It's interesting to know that not all women develop cystitis at the same time in their cycle. Certain phases are particularly prone to infections, and identifying these periods of vulnerability can help you better protect yourself.

Many women develop cystitis even before their period arrives, during premenstrual syndrome. This period generally starts 5 to 7 days before bleeding and corresponds to a gradual drop in estrogen. Consequently, your immune defenses are already beginning to decline, and if you add to that fatigue, mood swings, or cravings typical of PMS, you create a favorable context for infections.

This is obviously the riskiest time. The pH imbalance, constant humidity due to menstrual flow, the use of sanitary protection, and hormonal drop are at their maximum. If you are prone to urinary tract infections, it is often at this precise moment that they occur.

Some women notice that they develop cystitis in the middle of their cycle, at the time of ovulation. This is less common than during menstruation, but it does happen.

At this time, vaginal secretions change texture and become more abundant, which can temporarily alter the balance of the flora. Sexual intercourse is also often more frequent during this fertile period, which may explain this increased vulnerability in some women.

To better understand these at-risk moments, visualize your cycle as a curve:

• Days 1 to 5 (period): very high risk
• Days 6 to 12: low risk, your defenses are recovering
• Days 13 to 15 (ovulation): moderate risk for some women
• Days 16 to 24: low risk
• Days 25 to 28 (premenstrual phase): high risk

Of course, these markers vary depending on the length of your cycle. The idea is to identify your own period of vulnerability to strengthen your prevention at these specific times.

Beyond the natural mechanisms of the cycle, certain behaviors or habits can significantly increase your risk of developing cystitis during your period.

As we saw earlier, sanitary products can play a role, and not changing them regularly is probably the most common aggravating factor. A pad or tampon left in for too long becomes a real breeding ground for bacteria.

The rule: change your sanitary products every 3 to 4 hours maximum, even if your flow is not heavy. For menstrual cups, do not exceed 8 hours. Stagnant moisture combined with body heat creates ideal conditions for bacterial proliferation.

During their period, many women drink less, either from lack of desire or to avoid going to the toilet too often. Big mistake. Concentrated urine irritates the bladder and provides fewer opportunities to flush out bacteria. Drinking regularly (at least 1.5 liters of water per day) naturally "flushes" your urinary system and eliminates bacteria before they settle in. This is even more important during your period.

Tampons and menstrual cups don't cause problems for all women, but some are more sensitive to them. A tampon can put pressure on the urethra or absorb not only blood but also protective vaginal secretions, which dries out the mucous membranes.

As for cups, they can irritate if poorly positioned. If you find that your cystitis systematically occurs when you use these internal products, try switching to pads for a few cycles to see if it makes a difference.

Periods are often accompanied by physical fatigue, pain, sleep disturbances, and sometimes emotional stress. All of this further weakens your immune system, which is already challenged by hormonal variations. If you combine short nights, busy days, and an unbalanced diet during your period, you multiply your chances of getting sick. A fertile ground for the appearance of cystitis.

Read also: Remedies to relieve cystitis >

Despite all your precautions, cystitis can still rear its head. Here's how to react quickly to limit the damage.

Cystitis generally manifests as urgent and frequent urges to urinate, burning or pain when urinating, sometimes lower abdominal pain, and cloudy or foul-smelling urine. You may also feel like you never completely empty your bladder.

During your period, these symptoms can be confused with classic menstrual pain, so pay attention. If your urine contains blood (other than menstrual blood), if you have a fever or lower back pain, consult a doctor quickly as the infection could have reached the kidneys.

Don't let cystitis linger, thinking it will pass. Even during your period, consult your doctor as soon as the first symptoms appear.

A urine culture (ECBU) will confirm the infection and identify the responsible bacteria. Your doctor will probably prescribe an appropriate antibiotic.

Some pharmacies now offer rapid tests and can dispense treatment in certain cases; inquire. The faster you act, the sooner you'll feel relieved.

While waiting for treatment or its activation, you can relieve the symptoms of cystitis.

Drink plenty of water to dilute urine and calm burning sensations.

You can apply cold perineal packs (to be frozen before use) to relieve the burning sensation.

Apply a warm hot water bottle to the lower abdomen to soothe pain.

You can take paracetamol or an anti-inflammatory (if you have no contraindications). Avoid acidic, spicy foods, coffee, and alcohol, which further irritate the bladder.

Some women find relief with heather or bearberry teas, known for their soothing properties on the urinary tract.

As for supplements, cranberry capsules help limit the adhesion of bacteria to the bladder, while probiotics support your vaginal and urinary flora during the infection.

• Study name: The Vaginal Microbiome: Rethinking Health and Disease

• Link: Consult the study on Annual Reviews

• Major takeaway: This study explains how estrogens promote glycogen production, which is the exclusive "food" for Lactobacilli. When hormones drop during menstruation, the Lactobacilli population decreases, leaving the field open for pathogenic bacteria like E. coli.

• Study name: Fluctuations in the vaginal microbiome during the menstrual cycle

• Link: Consult the study on PubMed

• Major takeaway: Researchers observed that bacterial diversity increases during menstruation because blood (pH 7.4) neutralizes the usual protective acidity. It is during this precise window that intestinal bacteria most easily migrate to the urethra.

• Study name: Recurrent Urinary Tract Infections in Women: Risk Factors and Management

• Link: Consult the scientific publication

• Major takeaway: This study highlights the reduced "migration distance" in women (4 cm urethra) and demonstrates that humidity linked to sanitary products acts as a transport vector for fecal bacteria towards the bladder opening.

• Study name: The impact of tampons on the vaginal microbiome and epithelial health

• Link: Study on mucosal health

• Major takeaway: Research indicates that internal sanitary products can alter the local microflora by absorbing protective fluids or through micro-irritations, creating "entry points" for urinary tract infections if not changed every 4 hours.

In summary, cystitis during menstruation affects many women and is explained by several biological factors:

• the drop in estrogen weakens natural defenses,
• vaginal pH becomes unbalanced on contact with menstrual blood,
• the immune system slows down,
• and the anatomical proximity between the urethra and vagina facilitates bacterial migration.

Sanitary products can also irritate mucous membranes.

These infections mainly occur during and just before menstruation (premenstrual phase), sometimes during ovulation. Certain behaviors increase the risk: infrequently changed sanitary products, dehydration, fatigue, and stress.

In case of cystitis, you should consult a doctor quickly, drink plenty of water, relieve pain with a hot water bottle and paracetamol, and continue to protect yourself with gentle sanitary products.

And one action that can save you: supplements like cranberry and probiotics can provide additional relief!

Good luck 💚