We all have bad habits we know we should break. However, we don’t always realize how dangerous some of our habits can be. And, when it comes to our immune system, we don’t always realize how one bad habit could lead to a health problem.

Our immune systems are quite fragile, and even seemingly minor things can hamper them, making us more susceptible to illness and fatigue. In order to keep your immune system in tip-top shape to prevent colds and more serious illnesses, work on breaking these five bad habits.

1. Smoking

Smoking is one of the worst things you can do to your body, but particularly your immune system. Cigarettes as well as other chemical-based smoking devices like vape pens contain lots of chemicals and tar that can weaken the immune system and make it less effective. These chemicals can also destroy antibodies in the blood, which are necessary to fight off illness.

Smoking also causes inflammation throughout the body. This keeps the body in a persistent state of stress, causing your white blood cell count to remain elevated and your immune system to be weakened. A consistently high white blood cell count can also lead to larger health issues down the road.

Additionally, cigarettes can damage the linings of your mouth, nose and throat, which are actually crucial parts of your immune system. Studies have even showed that smoking can cause the immune system to attack your own lung tissue, causing even more problems.

2. Eating lots of sugar

Many people associate eating sugary foods with weight gain and an increased risk of obesity. While these risks are valid, what you may not know is that sugar can put a huge damper on your immune system, too.

The majority of your immune system resides in your gut. This means that whatever you eat has the potential to affect the microorganisms that live in your colon and, by extension, your immune system. Both good and bad bacteria live in the gut and regulate your digestive tract. A diet filled with sugar feeds those bad bacteria, allowing them to multiply and thrive. Harmful bacteria can end up overpowering the good bacteria, causing digestive problems in addition to a weakened immune system.

In order to keep your immune system in good shape, you must eat a balanced diet of helpful vitamins and nutrients and stay away from sugar-loaded snacks. If you need to satisfy your sugar cravings, swap sugary junk food for healthier alternatives like fruit or unsweetened dark chocolate. Natural sources of sugar are okay as long as you enjoy them in moderation.

3. Drinking alcohol

Alcohol is known for delivering brutal hangovers and negative symptoms, but regularly drinking alcohol can also have long-term effects on your immune system. Drinking can actually wear down the linings of your mouth and throat. Bacteria and viruses can find their way into the damaged lining and make you sick.

Alcohol also deprives your body of necessary nutrients like vitamins A and C. Over time, alcohol can make it more difficult for the body to operate properly, including the liver and white blood cells. This reduces overall health and wellness.

Alcohol can also destroy immune cells in various parts of the body. It can damage the fine hairs that are responsible for transporting pathogens out of the airways. Alcohol increases inflammation, which can harm the immune cells living in your gut.

If you are constantly fatigued or contract recurring infections, you may benefit from cutting back on your alcohol consumption. According to the CDC, the average woman should limit herself to one alcoholic beverage per day. Women who use drinking as a form of relaxation should consider alternative activities like yoga, journaling, spending time in nature or hanging out with friends.

4. Staying up too late

When life gets busy, sleep is often one of the first things to be sacrificed. Unfortunately, staying up late and cutting back on the number of hours you sleep each night might be setting you up for failure and sickness.

Your immune system needs sleep to help the body recharge and fight off any harmful pathogens that might be lurking inside. When you start becoming sleep deprived, the immune system is weakened and is less effective at keeping you healthy.

Let’s say you’re staying up late but sleeping in the next day, and you’re getting your full seven to eight hours. This can still mess with your body’s natural cycle. We all have an internal body clock called a circadian rhythm that dictates when it’s time to wake up and go to sleep. It’s best to keep this cycle consistent rather than fight it. Staying up really late one night but turning in early the next can disrupt your natural sleep cycle, making it harder for your body to fall and stay asleep and potentially setting you up for future sleep problems (and future immunity issues!).

5. Too many lounge days inside

After a busy work week or stressful time, it can be tempting to spend day after day lounging on the couch and not leaving the house. However, both holing up away from the sun and avoiding exercise can make you more susceptible to getting sick.

Getting outside in the sunlight is necessary to soak up some vitamin D, which you need to activate your immune system. Without vitamin D, the immune system can be suppressed and not as effective.

Additionally, staying active is critical for a healthy immune system. Studies show that routine exercise can bolster your immune system by improving white blood cell production and circulation. Working out is also instrumental in improving other healthy habits, like good sleep and stress reduction, which can play into a healthy immune system.

Focus on well-rounded health

In order to keep your immune system robust and healthy, focus on kicking these bad habits and implementing healthy routines that make you feel good. Drink lots of water, eat balanced and nutritious meals, get seven to eight hours of sleep each night, exercise and relieve stress to become a happier, healthier you.

Editor’s note: This blog was originally published in August 2019. It has been updated to include more relevant and comprehensive information.