Prioritizing your immune system has never been more important, especially with the highly contagious Omicron subvariant, BA.2, that is helping to drive another surge of Covid cases around the world.

As an immunologist and functional medicine doctor, patients often ask me how they can measure their immune system health. I tell them that our immune system is a moving target and has no real specified organs where it can be completely isolated. You can't scan it with an X-ray, biopsy it, or determine it's exact strength or weakness with a single test.

However, there are four major warning signs that can indicate whether you have a weakened immune system and should put extra effort into giving it a boost:

Signs you have a weak immune system

1. You get sick frequently and take longer than usual to recover.

Don't be alarmed if you get the sneezes and sniffles through two or three colds a year. Most people bounce back to normal in about a week.

But if you're constantly catching colds with symptoms that linger for weeks, or even get food poisoning often, it may be due to a sluggish response from your innate immune system.

Your innate immune system involves barriers that keep harmful materials from entering your body. Think of it as the first line of defense against all invaders and injury. Its components include:

• Cough reflex, which helps us expel things that may irritate or infect us.
• Mucus production, which traps bacteria and small particles and helps expel them from the body.
• Stomach acid, which helps kill microbes that enter through our food and water.

2. You are in a constant state of stress.

Certain types of stress can be beneficial for our immune health and overall wellness.

For example, a short-term acute stressor — like a traffic jam — is designed to help your body supercharge its protective mechanisms in an instant. Because of this, acute stress actually helps boost your immune system in the short term.

On the other end of the stress spectrum, chronic stress can be bad news, causing immune dysregulation and immune suppression, leading to increased infections and poor recovery from diseases.

Studies also show that frequent episodes of stress seem to exacerbate autoimmune diseases like rheumatoid arthritis and ulcerative colitis and can cause flare-ups in allergic reactions like eczema and asthma.

3. You get cold sores often, or had shingles at a young age.

The viruses that cause cold sores and shingles are both in the herpes virus family. Once you have contracted a herpes virus, it goes into a dormant state in the body.

However, when you are under stress or your cellular immunity weakens, the virus can replicate and reactivate again.

Seeing frequent reactivations can be a sign that your immune system needs a boosting.

4. You take medications that weaken your immune response.

Unfortunately, many important medications that are used in cancer chemotherapy — to prevent organ transplant rejection and to treat autoimmune diseases — can be immunosuppressive.

Corticosteroids, a common class of drugs used for allergies, asthma and other inflammatory diseases can also be immunosuppressive.

Even a history of frequent antibiotic use has been shown to damage microbiome diversity in the gut, which can directly impair immune responses.

How to strengthen your immune system

The good news is that regardless of the status of your immune resilience, you can intervene daily to make it stronger.

Here are some effective ways to do that:

1. Feed your immune system.

Our immune system cells require a wealth of antioxidant-rich foods — mostly fresh fruits and vegetables, especially those rich in vitamin C and beta-carotene.

Focus on getting daily servings of dark leafy greens like kale, deeply pigmented berries like blackberries and gut-friendly, fiber-rich cruciferous vegetables like cabbage, broccoli and arugula.

The minerals zinc and selenium are also powerful immune supportive nutrients and are found in nuts, seeds, shellfish and some meats.

Lastly, add in some superfoods like shitake and maitake mushrooms, green tea, and spices like turmeric, rosemary and cloves.

2. Get some sun.

In addition to improving your mood, just 10 to 15 minutes a day of full-spectrum light may provide adequate vitamin D, an important immune-supportive vitamin.

Some data indicates that low vitamin D is a risk factor for poor immune status, including autoimmune disease and Covid. So if you have weak immunity, it's a good idea to get your levels checked and supplement your time in the sun with vitamin D pills.

3. Focus on sleeping.

Quality and quantity of sleep has a major impact on immune resilience.

Chronic sleep deprivation is associated with higher inflammation and more frequent infections. This is because while our body is resting, the immune system cells can also focus all efforts and energy on a strong attack against viruses and bacteria.

Also, sleep enhances the formation of memory antibodies to bacteria and viruses, to help build a stronger immune system for the future.

4. Stop smoking.

This should be a no-brainer, but even the chemicals in secondhand and even thirdhand smoke are carcinogens. The damage that these products create in our tissues keeps us inflamed and in a constant state of repair.

Cigarettes, marijuana and vapes are all detrimental to the respiratory tract, which is the first barrier of entry for airborne viruses and bacteria.

5. Limit alcohol use.

Alcohol has negative effects on most our innate and adaptive immune cells.

Chronic and binge drinking also damages the lining of the gastrointestinal tract, as well as protective T cells and neutrophils in the GI system. This disrupts gut-barrier function and allows leakage of microbes into the blood, resulting in inflammation.

6. Double down on stress management.

Chronic, unmanaged emotional and physical stress elevates inflammatory cytokine release, and people who have high physical and emotional stressors have greater levels of inflammation.

In fact, C-reactive protein, which is a marker for inflammation, goes up in patients under acute stress.

One of the most effective ways to strengthen your immune response is to manage your stress through meditation, breathing exercises and other mindfulness activities.

Dr. Heather Moday is a board-certified allergist, immunologist and functional medicine physician. She is also the author of "The Immunotype Breakthrough: Your Personalized Plan to Balance Your Immune System, Optimize Health, and Build Lifelong Resilience." Follow her on Instagram @theimmunityMD and Facebook.

Don't miss:

• This is the ‘worst food ingredient for your immune system’—especially during Covid, says immunologist
• To ‘stay healthy and strong,’ a dietician eats these 5 staple foods of the Mediterranean diet
• A Harvard nutritionist shares the 6 best brain foods: ‘Most people aren’t eating enough of’ these

Sign up now: Get smarter about your money and career with our weekly newsletter