Frequent Infections: Why Do I Keep Getting Sick?

How many infections is normal?

It is common to feel you are "always sick" when colds overlap. Typical rates are:

Colds last 7 to 10 days, with a cough that can linger for 2 to 3 weeks, so two or three colds in a row can fill a whole winter. What matters more than the number is whether infections are severe, unusual, slow to clear or keep returning in the same place.

Everyday reasons for getting sick often

• High exposure: young children at home, working in schools, daycare or healthcare, public transport and crowded offices
• Poor sleep: people sleeping less than 6 to 7 hours catch colds more easily after exposure
• Chronic stress, which suppresses immune responses
• Smoking and vaping, which damage the airway's natural cleaning system
• Allergies and asthma: inflamed airways make infections more likely, and allergic symptoms are often mistaken for repeated colds
• Poor nutrition, heavy alcohol use, and low vitamin D
• Overtraining in endurance athletes
• Hand hygiene: touching the face after surfaces spreads viruses

Medical causes of recurrent infections

Secondary (acquired) immune problems

These are far more common than inherited conditions:

• Diabetes: high blood sugar impairs white blood cells, causing recurrent skin, urinary, gum and yeast infections
• HIV infection: may cause frequent or unusual infections, shingles, thrush and swollen nodes
• Medicines: steroids, chemotherapy, biologic drugs for arthritis or bowel disease, and transplant drugs
• Cancers of the blood and lymph system, such as leukemia, lymphoma and myeloma
• Neutropenia: a low count of infection-fighting white cells
• Chronic kidney or liver disease, and malnutrition
• No spleen (after surgery) or sickle cell disease, which raise the risk of severe bacterial infections

Structural or local problems

Infections that keep returning in one place usually have a local cause:

• Sinuses: chronic sinusitis, nasal polyps, a deviated septum or allergies
• Ears in children: large adenoids, a cleft palate or exposure to smoke
• Lungs: asthma, COPD, bronchiectasis, cystic fibrosis, a swallowing problem causing aspiration, or a blocked airway
• Urinary tract: anatomy, incomplete bladder emptying, kidney stones or menopause. See recurrent UTI
• Skin: eczema, carrying Staphylococcus aureus in the nose, or hidradenitis suppurativa

Primary (inherited) immune deficiency

Primary immunodeficiency is a group of more than 400 inherited conditions. Some, such as common variable immunodeficiency (CVID) and IgA deficiency, are first diagnosed in adults. Warning signs include:

• needing antibiotics often with little effect, or IV antibiotics to clear infections
• 2 or more pneumonias within a year
• deep skin or organ abscesses
• persistent thrush after age 1
• infections with unusual germs
• poor growth in a child
• a family history of immune deficiency or early deaths from infection

How doctors investigate frequent infections

Your doctor will review which infections you have had, how they were confirmed, how they were treated, how quickly they cleared, your vaccinations, medicines, lifestyle and family history. Keeping a diary of infections, test results and antibiotic courses is very helpful.

First tests usually include:

• Complete blood count with differential: checks white cell numbers and types
• Blood sugar or HbA1c for diabetes
• HIV test
• Kidney and liver function
• Immunoglobulin levels (IgG, IgA, IgM) and antibody responses to vaccines such as tetanus and pneumococcus

Depending on the pattern, you may need sinus CT, chest imaging, allergy testing, urine studies or referral to an immunologist.

Treatment

Treatment depends on the cause:

• control of blood sugar, asthma, allergies or reflux
• stopping smoking
• treating structural problems, such as sinus surgery or ear tubes
• antiretroviral treatment for HIV
• immunoglobulin replacement therapy for antibody deficiencies
• preventive antibiotics in selected cases
• staying up to date with vaccines, including flu, COVID-19 and pneumococcal vaccines where recommended

Reducing how often you get sick

• Wash hands with soap for 20 seconds, especially before eating and after being out
• Get 7 to 9 hours of sleep
• Stop smoking and limit alcohol
• Stay physically active
• Keep vaccinations up to date
• Stay home when sick, and avoid close contact with sick people where you can

Supplements such as vitamin C, zinc and echinacea have, at best, small effects on cold duration. Vitamin D supplements help mainly people who are deficient.

Frequently asked questions

Why do I keep getting sick?

Most often it is heavy exposure, such as living with young children or working with the public, combined with poor sleep, stress, smoking or untreated allergies. If infections are severe, unusual, slow to clear or need repeated antibiotics, see a doctor to check for diabetes, HIV or an immune problem.

What are the signs of a weak immune system?

Infections that are frequent, severe, last unusually long, return despite treatment or are caused by unusual germs. Needing IV antibiotics, repeated pneumonia, deep abscesses, persistent thrush and poor growth in children are key warning signs that warrant immune testing.

How many colds a year is normal?

Adults typically get 2 to 4 colds a year, and young children 6 to 8 or more, especially in their first years of daycare or school. Each cold lasts 7 to 10 days, so it can feel like constant illness in winter even when the immune system is normal.

What blood tests check the immune system?

The usual first tests are a complete blood count, immunoglobulin levels (IgG, IgA, IgM), antibody responses to vaccines, an HIV test, and blood sugar. An immunologist may add tests of specific immune cells and complement proteins depending on the type of infections.