Weak Immune System: What It Means and When to Seek Advice

After a run of colds or a stretch of feeling run down, people often feel they have a weak immune system. But it’s not that simple. From the start, you can't diagnose immune system conditions yourself. As the Australasian Society of Clinical Immunology (ASCIA) explains, everyone gets infections. If you get frequent infections, it doesn’t necessarily mean that your immune system is ‘weak’.

This article will explain what the immune system does, what ‘immunodeficiency’ means, how infections can look different when the immune system isn't working properly, and when you need to see your doctor. 

There are no checklists for immune system health, and the only way to know how your immune system is doing is to see a healthcare professional.

What Does the Immune System Do? 

In short, your immune system protects you. 

As Healthdirect explains, your immune system defends your body from infection, but things can go wrong. Healthdirect notes that sometimes the immune system doesn't work properly and can't protect your body as well as it should, which can increase your risk of getting an infection. This is what people usually think of when they talk about a weakened immune system. At other times, your immune system may overreact to something in your body or the environment, which is a different issue.  

What Is Immunodeficiency?

Immunodeficiency is the term Healthdirect uses for an underactive immune system: one that doesn't work properly and can't protect the body as well as it should.

Some forms of immunodeficiency are linked to a person's genes. ASCIA describes a group of conditions called inborn errors of immunity (IEI), which include primary immune deficiencies (PID). These are potentially serious chronic medical conditions that can lead to frequent or severe infections, swellings and autoimmune problems. These disorders cause the immune system to fail to work normally. These conditions require medical assessment and treatment. Catching contagious infections, however regularly or frequently, does not necessarily mean immunodeficiency. 

Patterns That May Warrant Medical Assessment

People often search online for symptoms of a weak immune system, hoping to find a clear list. But what matters more than symptoms is the pattern of infections over time, which a doctor weighs alongside your history when evaluating your immune health. ASCIA offers health patterns to watch for and discuss with your doctor if you have concerns about your immune system. These aren't a scoring system, and they don’t necessarily indicate that anything is wrong with your immune system. 

Recurrent, Severe or Persistent Infections

ASCIA strongly reassures us: everyone gets infections from time to time. Their resources explain that what’s different in people with PID or IEI disorders is that infections can be unusually persistent, recurrent or resistant to treatment, or unexpectedly severe.

Unusual Infections

ASCIA also notes that germs, including bacteria, viruses, fungi, or parasites, that aren’t usually problematic can cause infections in people with these PID or IEI disorders. Whether an infection is unusual is something your doctor will need to determine.  You can’t tell whether an infection is unusual on your own.

ASCIA also lists signs of immune system dysfunction for both children and adults, indicating that if someone has two or more of these signs, they should discuss their immune system health with their doctor.  We haven’t included these lists here, but you can look at them with your doctor if you have concerns about your immune system. 

What Can Cause Reduced Immune Function?

As  ASCIA explains, IEI and PID disorders can result from defects in genes that control the immune system and may be inherited. Other causes of immune system problems exist too, which your doctor will consider when reviewing your overall health, medical history, and the results of any relevant investigations or blood tests.

Everyday Habits and Normal Immune Function

It's natural to want to look after your immune system health yourself. Healthy eating supports overall health, including your immune system. The Australian Dietary Guidelines recommend eating a wide variety of nutritious foods from the five food groups every day, drinking plenty of water, and limiting foods high in saturated fat, added salt, added sugars, and alcohol.

That's sound advice for everyone, focused on overall health. Dietary changes don't 'boost' immunity or prevent infections, and they aren't a treatment for immunodeficiency.

When to Seek Advice or Urgent Care

If you're worried about how often you get infections, how severe they are or how long they last, talk to your GP. ASCIA suggests that if you have two or more of the signs it lists, you should discuss your immune system health and overall health history with your doctor. Your GP can work through this with you and investigate what’s happening. 

If you're already seeing a doctor or specialist about an immune system condition, keep following their advice. And if you or someone you know becomes seriously unwell, seek urgent medical care or call Triple Zero (000).

Frequently Asked Questions

How can I tell if my immune system is weak?

You can't tell if your immune system is weak from a single symptom or a home checklist.

As ASCIA communicates, everyone gets infections. If your infection pattern worries you, a doctor can help you assess it properly.

Does getting frequent colds mean immunodeficiency?

No, not on its own. 

ASCIA reminds us that everyone gets infections. If infections are unusually persistent, recurrent, resistant to treatment, unexpectedly severe, or caused by unusual germs, this could mean your immune system isn’t working properly. If you're concerned, your GP will assess you and investigate your health, which is much more accurate and specific than drawing your own conclusions.

Can foods fix immunodeficiency?

There is no known ‘quick fix’ for immunodeficiency, including foods.

The Australian Dietary Guidelines offer general nutrition guidance for overall health, which in turn can support immune system health.