How your menstrual cycle impacts your immune system.

Do you notice this too? Cycle day 10 - just before ovulation - and you're sitting on a bus full of coughing, sniffling people. Nothing happens to you. Your immune system beats every virus down. 

Just in time for your period, however, it's a completely different story. Every cold seems to jump out at you. If things go particularly badly, you have period pains, a fever and a sore throat all at the same time. 

In fact, this combination is anything but rare. And, according to scientists, this is no coincidence. 

Over the last 20 years, numerous studies have shown that your immune defenses actually decrease in the second half of your cycle, the luteal phase. In the time between ovulation and the start of your period, the immune response to pathogens is milder and you are more susceptible to infections during this time.

How do sex hormones influence your immune defense?

The interaction between hormones and a woman's immune system has not yet been fully researched. 

It is already known,though, that the high oestrogen level in the first phase of your cycle (follicular phase) causes certain changes in the immune system. Oestrogen interacts with the immune cells, among other things by docking onto their external receptors and influencing internal cellular processes. 

This interaction leads to inflammatory reactions and strengthens your defenses against potential pathogens1.

In general, girls and women statistically have a stronger immune system than men and boys. The differences are particularly great in the first half of the menstrual cycle. Unfortunately, the female part of the population is also more prone to autoimmune diseases and allergies, an undesirable side effect of this magnificent immune response2,3.

Why are you more susceptible to infections in the second half of your cycle?

Just in time for ovulation, oestrogen levels fall and progesterone levels rise. Testosterone also has an influence during this phase, the exact effects of which are still being researched. 

These processes gently downregulate your immune system. This regulation is strong enough to provide relief for many women with autoimmune diseases and at the same time prevent the body from misinterpreting and attacking a fertilized egg as a hostile pathogen. 

Unfortunately, this also allows some cold or intestinal viruses to reach their target2 and you get sick more quickly.

During the second phase of your cycle, the luteal phase, oestrogen and progesterone increase together. Shortly before your period, the levels of both hormones fall again. 

This drastically reduces your immune defenses for a short time. This is an advantage if you have just had a baby, but not so good if you are not expecting a child and are sitting on a bus or train full of sniffling contemporaries2.

How do sex hormones affect allergies?

Allergies are a common condition in which the immune system reacts excessively to normally harmless substances. It is known that hormones, especially sex hormones, have a significant influence on the immune system and thus on the tendency to have allergies5

What influence does the menstrual cycle have on allergies?

It's not just your immune response that varies over the course of your monthly cycle. The fluctuating hormone levels can also influence your allergy symptoms.

At the beginning of the cycle (follicular phase), when oestrogen levels are high, many women suffer from a runny nose and watery eyes. 

It is not only the particularly high hormone levels that can trigger allergies, but also the drop in hormones in the cycle shortly before your period. 

Many women report increased allergy symptoms shortly before menstruation and during the first few days of bleeding. These symptoms may occur in addition to mood swings and abdominal pain.

Oestrogen and its influence on allergies

Interestingly, studies show that more boys than girls are affected by allergies and asthma in childhood. 

However, this dynamic changes from around the age of 10. With the increased production of oestrogen during puberty, girls and women generally suffer more frequently and more intensively from allergies6.

Testosterone and the influence on allergies

In general, men have higher testosterone levels than women. In contrast to oestrogen, testosterone appears to have a protective effect and reduce allergic reactions7

As a result, young girls and women are not only more susceptible to allergies, but may also suffer more severe forms.

Improvement during the menopause

During and after menopause, oestrogen levels fall and many women report an improvement in their allergy symptoms8

The opposite is true for men. As testosterone levels fall with age, the frequency of allergies often increases.

Increased symptoms during pregnancy

During pregnancy, many women experience increased allergy symptoms, which is not surprising given the increased oestrogen production during this time. 

In the second trimester of pregnancy in particular, many complain of a blocked nose due to allergies. In addition, an existing asthma condition can worsen during pregnancy. 

In fact, it has been found that severe asthma attacks can increase by a third during this time. This is nothing to be alarmed about, but it is important that affected women discuss their condition with their doctor9

Fortunately, there are safe medications that can be used safely during pregnancy. Symptoms usually improve one to three months after giving birth.

a pregnant woman wearing white clothes, you can only see the pregnancy belly

What still needs to be researched

There is still a lot of research to be done on the menstrual cycle and hormones. Further research could also provide exciting findings in connection with the immune system.

Unfortunately, no study results are yet available that allow conclusions to be drawn about the menstrual cycle and vaccines. For example, it would be interesting to find out whether the immune response and vaccination reaction differ depending on the phase of the menstrual cycle.

Another interesting field of research concerns the effects of hormonal contraception on the immune system. The pill and other hormonal contraceptive methods contain artificial hormones whose long-term effect on the risk of infection is not yet fully understood.

Do permanently elevated levels of sex hormones mean fewer infections? Or, on the contrary, are there more? 

There are indications that some "pills" containing only progestin, an artificial progesterone, can reduce inflammatory reactions in the body to such an extent that susceptibility to infections increases1. Despite these findings, many questions in this area remain unanswered.

What can you do to support your body?

You can strengthen your immune system in all phases of your cycle, for example by eating a diet rich in vitamins and minerals, getting plenty of fresh air and exercise and getting enough sleep. 

It is important that you always pay attention to your own body's signals during your cycle. You can use cycle tracking, for example, to get to know your body better and assign your individual signals to the cycle phases.

Cycle computers such as Daysy help you to track your cycle based on your basal body temperature. You automatically receive practical information about the duration of your cycle, as well as the time of your ovulation and your period

A red background with white font. The slogan says: Daysy - Get to know your body today. On the left hand side is a white hardware device. It is the menstrual cycle tracker Daysy


1.) Alvergne A, Tabor VH: Is Female Health Cyclical? Evolutionary Perspectives on Menstruation. arXiv preprint arXiv:1704.08590. 2017 Apr 26.

2.) Maegan Boutot: The immune system and the menstrual cycle, Helloclue 2018.

3.) Oertelt-Prigione S. Immunology and the menstrual cycle. Autoimmunity reviews. 2012 May 31;11(6):A486-92,

4.) Cunningham M, Gilkeson G. Estrogen receptors in immunity and autoimmunity. Clinical reviews in allergy & immunology. 2011 Feb 1;40(1):66-73.

5.) Fischer J, Jung N, Robinson N, et al. Sex differences in immune responses to infectious diseases. Infection. 2015;43:399–403. doi: 10.1007/s15010-015-0791-9. PubMed

6.) RKI

7.) Pharmazeutische Zeitung

8.) Popular Science [Internet]. How long do allergies last—a few years or your whole life? 2021 May 14. Available from: