Immune health basics

Sources

Every numbered claim on the overview and article pages is listed here with the exact passage it rests on. 46 passages were checked word-for-word against the saved copies listed below.

Pharmacist review pending46 verified passagesUpdated 2026-10-22

Current evidence

1

The immune system's job is to prevent or limit infection.

“The overall function of the immune system is to prevent or limit infection.”

NIAID (U.S. National Institutes of Health) — Overview of the Immune SystemPassage verified word-for-word in saved copy
2

Too little immune response leads to infection; too much, or one that will not switch off, leads to allergies and autoimmune disease.

“If an immune response cannot be activated when there is sufficient need, problems arise, like infection. On the other hand, when an immune response is activated without a real threat or is not turned off once the danger passes, different problems arise, such as allergic reactions and autoimmune disease.”

NIAID (U.S. National Institutes of Health) — Overview of the Immune SystemPassage verified word-for-word in saved copy
3

Common infections such as influenza can temporarily suppress the immune system.

“Common infections, including influenza and mononucleosis, can suppress the immune system.”

NIAID (U.S. National Institutes of Health) — Disorders of the Immune SystemPassage verified word-for-word in saved copy
4

Autoimmune diseases happen when the immune system attacks the body's own cells.

“Autoimmune diseases occur when self-tolerance is broken.”

NIAID (U.S. National Institutes of Health) — Disorders of the Immune SystemPassage verified word-for-word in saved copy
5

Vaccines teach your immune system to recognize and defend against harmful germs.

“Vaccines are injections (shots), liquids, pills, or nasal sprays that you take to teach your body's immune system to recognize and defend against harmful germs.”

MedlinePlus (U.S. National Library of Medicine) — VaccinesPassage verified word-for-word in saved copy
6

The immune system remembers the germ and attacks it if it invades again.

“Your immune system also remembers the germ. It will attack the germ if it ever invades again.”

MedlinePlus (U.S. National Library of Medicine) — VaccinesPassage verified word-for-word in saved copy
7

Vaccines teach the body to defend itself without the dangers of a full infection; any tiredness lasts a day or two, and the protection can last a lifetime.

“Vaccines help the body learn how to defend itself from disease without the dangers of a full-blown infection.”
“The immune response to a vaccine might cause tiredness and discomfort for a day or two, but the resulting protection can last a lifetime.”

U.S. Centers for Disease Control and Prevention — Explaining How Vaccines WorkPassage verified word-for-word in saved copy
8

A vaccinated person is far less likely to die or become seriously ill than someone unprotected.

“But a vaccinated person is far less likely to die or become seriously ill than someone whose immune system is unprepared to fight an infection.”

U.S. Centers for Disease Control and Prevention — Explaining How Vaccines WorkPassage verified word-for-word in saved copy
9

Adults should get a tetanus booster every 10 years or during each pregnancy.

“Adults should get a tetanus booster once every 10 years or during each pregnancy.”

U.S. Centers for Disease Control and Prevention — Explaining How Vaccines WorkPassage verified word-for-word in saved copy
10

Almost everyone 6 months and older should get a flu vaccine every season.

“Everyone 6 months and older in the United States, with rare exception, should get a flu vaccine every season.”

U.S. Centers for Disease Control and Prevention — Key Facts About Seasonal Flu VaccinePassage verified word-for-word in saved copy
11

CDC estimates that in the 2024–2025 season flu vaccination prevented 10 million illnesses, 180,000 hospitalizations and 12,000 deaths in the U.S.

“For example, during the 2024–2025 flu season, CDC estimates that flu vaccination prevented 10 million flu-related illnesses, 5 million flu-related medical visits, 180,000 flu-related hospitalizations, and 12,000 flu-related deaths in the United States”

U.S. Centers for Disease Control and Prevention — Benefits of Flu VaccinationPassage verified word-for-word in saved copy
12

In older adults, flu vaccination reduced the risk of flu hospitalization by about 40% on average in one review.

“A 2017 systematic review found that during the 2010–2011 through 2014–2015 flu seasons, flu vaccination reduced the risk of flu-related hospitalization among older adults by about 40% on average.”

U.S. Centers for Disease Control and Prevention — Benefits of Flu VaccinationPassage verified word-for-word in saved copy
13

Handwashing reduces respiratory illnesses such as colds by 16% to 21%, and diarrhea by 23% to 40%.

“Reduces respiratory illnesses, like colds, in the general population by 16-21%”
“Reduces the number of people who get sick with diarrhea by 23-40%”

U.S. Centers for Disease Control and Prevention — Handwashing FactsPassage verified word-for-word in saved copy
14

Scrubbing for at least 20 seconds removes more germs than shorter washing.

“Scrubbing your hands for at least 20 seconds removes more germs from hands than washing for shorter periods”

U.S. Centers for Disease Control and Prevention — Handwashing FactsPassage verified word-for-word in saved copy
15

If you are short of sleep, you may have trouble fighting common infections.

“For example, if you're sleep deficient, you may have trouble fighting common infections.”

NHLBI (U.S. National Institutes of Health) — Sleep Deprivation and Deficiency — How Sleep Affects Your HealthPassage verified word-for-word in saved copy
16

Smoking causes problems of the immune system, among many diseases; quitting is one of the most important things you can do for your health.

“Other diseases, including certain eye diseases and problems of the immune system, including rheumatoid arthritis.”
“Quitting smoking is one of the most important actions people can take to improve their health.”

U.S. Centers for Disease Control and Prevention — Cigarette SmokingPassage verified word-for-word in saved copy
17

Zinc lozenges or syrup may speed recovery from a cold if started at the very beginning, but do not seem to make symptoms milder.

“Some studies suggest that zinc lozenges or zinc syrup speeds recovery from the common cold if you start taking them at the start of a cold. However, these products don't seem to affect the severity of cold symptoms.”

NIH Office of Dietary Supplements — Zinc — Fact Sheet for ConsumersPassage verified word-for-word in saved copy
18

Zinc used in the nose, such as gels and swabs, has been linked to long-lasting or permanent loss of smell.

“Zinc products used in the nose (such as nasal gels and swabs) have been linked to a long-lasting or even permanent loss of the sense of smell”

NCCIH (U.S. National Institutes of Health) — Colds and Flu and Complementary Health ApproachesPassage verified word-for-word in saved copy
19

Too much zinc can cause nausea and vomiting, and over a long time can lower immunity.

“Signs of too much zinc include nausea , dizziness, headaches, upset stomach, vomiting, and loss of appetite.”
“If you take too much zinc for a long time, you could have problems such as lower immunity”

NIH Office of Dietary Supplements — Zinc — Fact Sheet for ConsumersPassage verified word-for-word in saved copy
20

Vitamin C does not prevent colds in the general population and shortens them only slightly.

“concluded that taking vitamin C doesn’t prevent colds in the general population and shortens colds only slightly”

NCCIH (U.S. National Institutes of Health) — Colds and Flu and Complementary Health ApproachesPassage verified word-for-word in saved copy
21

Echinacea has not been convincingly shown to help colds.

“A comprehensive 2014 assessment of this research concluded that echinacea hasn’t been convincingly shown to be beneficial.”

NCCIH (U.S. National Institutes of Health) — Colds and Flu and Complementary Health ApproachesPassage verified word-for-word in saved copy
22

Honey may reduce nighttime coughing in children, but never give honey to a baby under 1 year.

“A small amount of research suggests that honey may help to decrease nighttime coughing in children.”
“Honey should never be given to infants under the age of 1 year because it may contain spores of the bacterium that causes infant botulism.”

NCCIH (U.S. National Institutes of Health) — Colds and Flu and Complementary Health ApproachesPassage verified word-for-word in saved copy
23

Probiotics might reduce colds, but the quality of the evidence is low or very low.

“found some evidence suggesting that probiotics might reduce the number of colds or other upper respiratory tract infections that people catch and the length of the illnesses, but the quality of the evidence was low or very low.”

NCCIH (U.S. National Institutes of Health) — Colds and Flu and Complementary Health ApproachesPassage verified word-for-word in saved copy
24

Vitamin C from food helps the immune system work properly.

“helps the immune system work properly to protect the body from disease”

NIH Office of Dietary Supplements — Vitamin C — Fact Sheet for ConsumersPassage verified word-for-word in saved copy
25

Zinc helps the immune system fight bacteria and viruses.

“It helps your immune system fight off invading bacteria and viruses .”

NIH Office of Dietary Supplements — Zinc — Fact Sheet for ConsumersPassage verified word-for-word in saved copy
26

Trouble breathing, chest pain, confusion or bluish lips with a fever or flu — call 911.

“Contact your provider right away if you or your child have:”
“Difficulty breathing”
“Any breathing problems are an emergency. Seek medical help right away.”

MedlinePlus (U.S. National Library of Medicine) — FluPassage verified word-for-word in saved copy
27

Trouble breathing, chest pain, confusion or bluish lips with a fever or flu — call 911.

“Call 911 or the local emergency number if:”
“You have sudden crushing, squeezing, tightening, or pressure in your chest.”

MedlinePlus (U.S. National Library of Medicine) — Chest painPassage verified word-for-word in saved copy
28

Swelling of the face or throat, or trouble breathing, soon after a vaccine or medicine — call 911.

“Contact 911 or the local emergency number for medical assistance right away if:”
“The person is having a severe allergic reaction. Do not wait to see if the reaction is getting worse.”

MedlinePlus (U.S. National Library of Medicine) — Allergic reactionsPassage verified word-for-word in saved copy
29

Swelling of the face or throat, or trouble breathing, soon after a vaccine or medicine — call 911.

“Difficulty breathing, coughing, wheezing, or high-pitched breathing sounds”
“Swelling of the face, eyes, or tongue”

MedlinePlus (U.S. National Library of Medicine) — AnaphylaxisPassage verified word-for-word in saved copy
30

Fever while on chemotherapy or other immune-suppressing treatment — call your care team now.

“Call your health care team if you have signs of an infection. Infections during cancer treatment can be life threatening and require urgent medical attention.”

National Cancer Institute (U.S. National Institutes of Health) — Infection and Neutropenia during Cancer TreatmentPassage verified word-for-word in saved copy
31

Fever while on chemotherapy or other immune-suppressing treatment — call your care team now.

“Contact your provider right away if you are on chemotherapy or corticosteroids and you develop:”
“A fever of 100.5°F (38°C) or higher”

MedlinePlus (U.S. National Library of Medicine) — Immunodeficiency diseasesPassage verified word-for-word in saved copy
32

Flu symptoms that are very bad and not getting better, or an illness that improves and then gets worse — contact your provider.

“Also contact your provider if flu symptoms are very bad and not getting better.”

MedlinePlus (U.S. National Library of Medicine) — FluPassage verified word-for-word in saved copy
33

Flu symptoms that are very bad and not getting better, or an illness that improves and then gets worse — contact your provider.

“Cold or respiratory illness that has been getting better and then begins to get worse”

MedlinePlus (U.S. National Library of Medicine) — SinusitisPassage verified word-for-word in saved copy
34

Infections that keep coming back, are unusually severe, or will not clear — contact your provider and ask whether an immune problem could be the cause.

“Contact your provider if you have repeated yeast infections or oral thrush .”

MedlinePlus (U.S. National Library of Medicine) — Immunodeficiency diseasesPassage verified word-for-word in saved copy
35

Infections that keep coming back, are unusually severe, or will not clear — contact your provider and ask whether an immune problem could be the cause.

“Primary immune deficiency diseases (PIDDs) are inherited genetic disorders and tend to cause chronic susceptibility to infection.”

NIAID (U.S. National Institutes of Health) — Disorders of the Immune SystemPassage verified word-for-word in saved copy

Source documents

NIAID (U.S. National Institutes of Health) — Overview of the Immune System
Saved 2026-10-19 · download · SHA-256 146610d2903e385e…
NIAID (U.S. National Institutes of Health) — Disorders of the Immune System
Saved 2026-10-19 · download · SHA-256 fce7186e126f8265…
U.S. Centers for Disease Control and Prevention — Explaining How Vaccines Work
Saved 2026-10-19 · download · SHA-256 6225fd009986e7eb…
MedlinePlus (U.S. National Library of Medicine) — Vaccines
Saved 2026-10-19 · download · SHA-256 adf52ba246b65bad…
U.S. Centers for Disease Control and Prevention — Key Facts About Seasonal Flu Vaccine
Saved 2026-10-19 · download · SHA-256 1b4ddc44750b2500…
U.S. Centers for Disease Control and Prevention — Benefits of Flu Vaccination
Saved 2026-10-19 · download · SHA-256 818b74e27f787f58…
U.S. Centers for Disease Control and Prevention — Handwashing Facts
Saved 2026-10-19 · download · SHA-256 8fb05d7f98f0fa88…
U.S. Centers for Disease Control and Prevention — Cigarette Smoking
Saved 2026-10-19 · download · SHA-256 a9c65ecd49a0546b…
NHLBI (U.S. National Institutes of Health) — Sleep Deprivation and Deficiency — How Sleep Affects Your Health
Saved 2026-10-19 · download · SHA-256 3eec1595c1799c72…
NCCIH (U.S. National Institutes of Health) — Colds and Flu and Complementary Health Approaches
Saved 2026-10-19 · download · SHA-256 d1e69ea661fb89c7…
NIH Office of Dietary Supplements — Zinc — Fact Sheet for Consumers
Saved 2026-10-19 · download · SHA-256 1ca817bc557b3ace…
NIH Office of Dietary Supplements — Vitamin C — Fact Sheet for Consumers
Saved 2026-10-19 · download · SHA-256 99c7f59523ee6990…
MedlinePlus (U.S. National Library of Medicine) — Flu
Saved 2026-10-22 · download · SHA-256 09835f633673209d…
MedlinePlus (U.S. National Library of Medicine) — Chest pain
Saved 2026-10-22 · download · SHA-256 368b80496c551edb…
MedlinePlus (U.S. National Library of Medicine) — Allergic reactions
Saved 2026-10-22 · download · SHA-256 95cbda5c238330f1…
MedlinePlus (U.S. National Library of Medicine) — Anaphylaxis
Saved 2026-10-19 · download · SHA-256 9c5e351b864ae6e1…
National Cancer Institute (U.S. National Institutes of Health) — Infection and Neutropenia during Cancer Treatment
Saved 2026-10-22 · download · SHA-256 2779e8ce66aeb0d3…
MedlinePlus (U.S. National Library of Medicine) — Immunodeficiency diseases
Saved 2026-10-22 · download · SHA-256 a699d753648e5db6…
MedlinePlus (U.S. National Library of Medicine) — Sinusitis
Saved 2026-10-19 · download · SHA-256 118b218228fe2e6a…

Historical perspective: Dr. Majid Ali archive

Historical perspective drawn from the authorized writings of Dr. Majid Ali, preserved in the Clarkson archive. Shown for context; it is not current medical guidance.

Protecting Your Immune System 2014-12-19
Source of the quoted line. His acid-alkaline claims in the same piece are held.
Flu Vaccine Denial Guilt 2015-01-11
Named so the archive is transparent. His vaccine scepticism is not carried in any form.

Claims we deliberately did not carry

His scepticism about vaccines, including pieces titled "Flu vaccine denial guilt" and "Flu Shot and Fear Withdrawal Syndrome", and his COVID-19-era writing.
A vaccinated person is far less likely to die or become seriously ill,⁸ and almost everyone 6 months and older should get a flu vaccine every season.¹⁰ Not carried in any form.
His claims that immune cells "love an alkaline environment" and that disease thrives on acid.
Not supported by the sources used here. Not carried.

Safety wording awaiting sign-off

The 'When to get help now' list is ProperHealth safety wording. Each line cites the official guidance it follows, and those passages are listed above with the other claims. The wording still needs pharmacist sign-off before public use.