9 Signs of a Weak Immune System (& How to Boost)

Updated in January 2024

A weak immune system is characterized by immunity that is unable to respond effectively to infections to fight them off. This can happen due to nutritional deficiencies, the use of certain medications or the presence of diseases that affect immunity, such as AIDS, lupus or cancer.

A weak immunity can be suspected when infections recur frequently, as this indicates that the immune system is unable to fight off infectious agents such as viruses and bacteria, which are the cause of colds, flu and more serious infections.

The immune system is a set of organs, tissues and cells that act to fight off harmful microorganisms and prevent diseases from developing.

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Signs of a weak immune system

When immunity is low, symptoms can appear such as:

  • Recurrent infections, such as tonsillitis or herpes
  • Simple illnesses that take a long time to go away or get worse easily
  • Frequent fever and chills
  • Frequently dry eyes
  • Excessive tiredness
  • Nausea and vomiting
  • Diarrhea for more than 2 weeks
  • Red or white spots on the skin
  • Severe hair loss

If you notice any of these symptoms, it's important to adopt measures that strengthen immunity, such as eating a healthy diet, for example, since some foods are able to strengthen and stimulate the body's defense cells. See what to eat to boost immunity.

What causes a weak immune system?

A weak immune system can occur due to a variety of situations, such as stress and anxiety, or chronic diseases (like AIDS, lupus, cancer and diabetes). These conditions can decrease the activity of the immune system and promote the appearance of other diseases.

The use of immunosuppressive drugs, corticosteroids or antibiotics can also weaken the immune system. It is important to tell your doctor if you notice any of the above systems after starting a new medication. The doctor may discontinue it or consider an alternative to avoid compromising the functioning of the body's defense cells.

Immunity can also be compromised by lifestyle habits such as a lack of physical activity, alcoholism, smoking and unhealthy eating.

Low immunity in pregnancy

During pregnancy, it's normal for the immune system to be weakened due to hormonal changes and changes in the woman's body. Extra care should be taken to avoid infections like the flu and UTIs.

To promote optimal health, pregnant women should attend all prenatal appointments, eat a diet rich in antioxidant-rich fruits and vegetables, such as oranges, pineapples, lemons, carrots and cabbage, and get their flu vaccine. 

How to boost immunity

To boost immunity, it's important to exercise regularly and improve your eating habits. You should opt for foods that stimulate the immune system, such as Brazil nuts, fish, carrots and spinach.

If you often have symptoms of low immunity, and if you additionally have risk factors that weaken the body's defense system, it is important to see your doctor. The doctor will identify the underlying cause and help to guide treatment. He or she may order bloodwork, and recommend the use of home remedies, such as echinacea tea, as a way of complementing the treatment for low immunity.

Vitamins for low immunity

Some vitamins and minerals that may be indicated in the case of low immunity are:

  • Vitamin C
  • Vitamin E
  • Vitamin A
  • Omega 3
  • Zinc
  • Selenium

These supplements can be taken on their own or as part of a multivitamin, and it is important to consult your doctor to determine the appropriate dose, which will vary depending on your needs and health history.