You can't boost your immune system overnight, but you can strengthen it with some simple lifestyle changes.
When done consistently for several weeks, drinking lots of water, getting enough sleep, and taking vitamin c and zinc supplements can help boost your immune system.
Some products might claim to boost your immunity quickly but maintaining a healthy lifestyle is the only way to strengthen your immune system long-term.

When it's working properly, your immune system is an internal defense against harmful germs and infections. However, building a strong immune system doesn't happen overnight.

In fact, strengthening your immune system can take weeks, according to Tulip Jhaveri, MD, a medical microbiology fellow at Brigham and Women's Hospital who specializes in infectious diseases.

Therefore, a shot of lemon-ginger juice isn't going to protect you from an infectious disease if you already have a weakened immune system. To boost your immune system quickly, you'll need to plan ahead and consistently follow some general guidelines for at least several weeks.

Can you improve your immune system in 24 hours?
If you have a weakened immune system, you will not be able to make a reasonable change in 24 hours.

The immune system is a complex system that requires many different working parts. Because of that, "there is no quick way to improve it," says Jhaveri.

That said, if you're looking for the fastest way to give your immune system the best chance of preventing infection, Jhaveri says that drinking plenty of water and getting enough sleep are critical.

But it's important to note that, "it typically takes weeks of regular intervention to have any impact," Jhaveria says.

How to strengthen your immune system
If you anticipate being in a situation where you may be exposed to a lot of germs - like if you're taking a flight soon - and want to take measures to protect yourself, here are five ways to boost your immunity:

Drink plenty of water
"Drinking plenty of water before a flight is important because the higher the altitude, the more the humidity drops, causing considerable loss of fluid," says Jhaveri.

To function properly, your immune system relies heavily on the nutrients in your bloodstream, which mostly consists of water. Without water, the cells and tissues of your immune system don't receive the nutrients they need. Your immune system also relies on water to flush out germs and waste materials.

The amount of water you need can vary; however you should aim to drink fluids regularly over the course of the day.

Get enough sleep
"Sleep is also very important as it enables the body to repair itself and get ready for the next day," says Jhaveri.

According to a 2017 study, sleep deprivation makes your body vulnerable to a lot of infectious agents. You should aim to get seven to eight hours of sound sleep a night to help boost immunity.

If you're about to take a trip, Jhaveri recommends avoiding caffeine right before and during your flight because it can dehydrate and disrupt your sleep schedule.

Exercise
Exercising may help flush germs out of your lungs and airways, reducing your chances of getting sick. It also stimulates your immune system and fights stress hormones that can make you ill.

If you can, try and do some moderate or vigorous exercise for 60 minutes several days a week for several weeks. You can opt for a brisk walk or a bicycle ride around your neighborhood.

Take vitamin C and zinc
Both vitamin C and zinc improve your defenses against pathogens and are critical for your immunity.

Deficiencies of these two nutrients are associated with more frequent and more severe cases of several illnesses, including malaria, diarrhea, the common cold, pneumonia, and other respiratory tract infections.

You can consult your doctor on whether you require these supplements and what dose is appropriate for you.

Have some bone broth
Chicken soup made with a bone broth may help clear your respiratory passageways and reduce inflammation, plus it's a pretty good source of protein, according to Harvard Medical School.

Though bone broth is a bit of a trend and evidence hasn't conclusively pointed to its benefits, protein is a critical nutrient for immunity since it is essential for the functioning of your T-cells, which are a type of white blood cell that play a major role in your immune response.

Long-term solutions to boost your immune system
To maintain a strong immune system long-term, it's important to lead a healthy lifestyle. Jhaveri recommends the following:

A healthy, balanced diet: Getting all the nutrients and energy you require can help ensure that all your cells, including those that make up your immune system, function well. Jhaveri personally suggests a plant-based diet that focuses on whole foods, because apart from improving your immunity, it can also reduce your risk of chronic diseases.
Regular exercise: Exercise stimulates your immune system and improves its ability to fight off viral communicable diseases, according to a 2020 study. "You can start with a 30-minute brisk walk three times a week to begin with, eventually increasing it to daily," says Jhaveri. The Centers for Disease Control and Prevention (CDC) recommends 150 minutes of exercise per week.
Healthy outlets to manage stress: Stress depresses your immune system and raises your risk of illness. "Meditation, connecting with family and friends (virtually, if necessary), practicing good sleep hygiene, and developing and following a set schedule can help reduce your stress levels," says Jhaveri.
Moderate alcohol intake: Alcohol compromises your immune system and makes it less effective at fighting infections. Jhaveri recommends eliminating alcohol from your diet altogether, if possible.
Not smoking: Like alcohol, smoking also impairs your immune system.
Insider's takeaway
Like the other systems in your body, your immune system is a complex network of processes that works best when you provide it sufficient energy and nutrition to function.

While several products claim to boost your immunity quickly, the most effective strategy is to consistently maintain a healthy lifestyle by eating a balanced diet, exercising regularly, reducing stress, and avoiding alcohol and smoking.

In fact, according to Jhaveri, "even multivitamins and multiminerals have minimal to no benefit in boosting immunity as was once believed - they're supplements, not substitutes to a well-balanced diet."

The best way to boost your immunity before a plane ride, or any other high-risk situation, is to get started on those healthy habits - hydration, nutrition, sleep, and exercise are your best bet.

And above all, maintain good hygiene: You can follow these guidelines by the CDC to protect yourself and others from infection:

Avoid close contact with people, especially if they're unwell.
Wash your hands with soap and water, or sanitize them with an alcohol-based solution.
Avoid touching your face.