CBSE Class 8 Science Revision Notes Chapter 3 Health: The Ultimate Treasure

Health is a state of physical, mental and social well-being, and not merely the absence of disease. Healthy habits, clean surroundings, disease prevention and immunity together support better health in India.

Health includes the proper functioning of the body, a calm and positive mind, and healthy relationships with others. A person may be free from disease but still feel unwell because of loneliness, stress or an unhealthy environment.

These CBSE Class 8 Science Revision Notes Chapter 3 cover healthy living, disease types, transmission, immunity, vaccines and antibiotics. The notes follow the current 2026–27 chapter for quick and structured revision.

Key Takeaways

• Three dimensions of health: Physical, mental and social well-being together define complete health.
• Disease types: Diseases may be communicable or non-communicable.
• Immunity: It is the natural ability of the body to resist and fight disease.
• Antibiotic rule: Antibiotics treat bacterial infections and do not work against viral diseases.

Access Class 8 Science Chapter 3 Health: The Ultimate Treasure Notes in 30 Minutes

Revise the chapter in three parts:

First 10 minutes: Meaning of health, healthy habits, environment, signs and symptoms
Next 10 minutes: Communicable diseases, non-communicable diseases and prevention
Final 10 minutes: Immunity, vaccines, antibiotics and antibiotic resistance

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Health in Class 8 Science Chapter 3 Notes

Health includes how we feel physically, mentally and socially. All three aspects affect our ability to study, work and handle difficult situations.

What Is Health?

The World Health Organization describes health as complete physical, mental and social well-being. It is more than being free from illness.

A healthy person can perform daily tasks efficiently. The person can also manage stress and adjust well with family, friends and society.

Physical Health

Physical health refers to the proper working of the body. It depends on nutrition, exercise, hygiene, rest and a clean environment.

Good physical health helps a person stay active and perform daily work without excessive tiredness.

Mental Health

Mental health includes thoughts, feelings and emotional well-being. Stress, loneliness, fear and excessive screen use can affect mental health.

Talking to family members, making friends, resting and seeking counselling can provide support.

Social Health

Social health refers to the ability to build and maintain healthy relationships. Spending time with family and friends supports emotional balance.

A person with good social health can communicate, cooperate and adjust with others.

Three Dimensions of Health

Ayurveda and Balanced Living

Ayurveda views health as a balance between the body, mind and surroundings. It suggests regular routines and healthy daily habits.

Important concepts include:

• Dinacharya: A balanced daily routine
• Ritucharya: Changes in routine according to seasons
• Prakriti: An individual’s body constitution

Fresh food, exercise, cleanliness, restful sleep, yoga and meditation support this balance.

Healthy Lifestyle in CBSE Class 8 Science Chapter 3 Notes

Health depends on lifestyle and environment. Daily habits can strengthen the body and mind or increase health risks.

Healthy Habits

Important healthy habits include:

• Maintaining personal hygiene
• Eating a balanced diet
• Exercising regularly
• Getting enough sleep
• Spending time outdoors
• Limiting screen time
• Relaxing or meditating
• Maintaining positive relationships

Unhealthy Habits

The following habits may harm physical and mental health:

• Eating fast food every day
• Consuming excessive sugar or fatty food
• Skipping meals
• Sleeping very late
• Getting insufficient sleep
• Spending too much time on screens
• Avoiding physical activity
• Using tobacco, alcohol or addictive drugs

Maintaining a Healthy Lifestyle

A healthy lifestyle includes a balanced diet with fruits, vegetables and whole grains. Processed, fatty and sugary food should be limited.

Physical activity may include walking, running, cycling, outdoor games or exercise. Yoga and breathing exercises such as pranayama may also support well-being.

Enough sleep allows the body and mind to rest and recover. Managing stress also improves concentration and emotional health.

Clean Environment and Health

Clean air, water and surroundings reduce exposure to disease-causing organisms. Dirty places may attract flies and mosquitoes.

Smoke and dust can make breathing difficult. Air pollution may contribute to coughing, asthma and other respiratory problems.

What Is AQI?

AQI stands for Air Quality Index. It indicates how clean or polluted the air is.

A higher level of air pollution can increase health risks, especially for people with breathing problems.

Signs, Symptoms and Diseases in Class 8 Science Revision Notes Chapter 3

Changes in the normal working of the body may indicate illness. Doctors use signs and symptoms to understand a health problem.

Difference Between Signs and Symptoms Class 8

A headache is a symptom because the patient feels it. A high body temperature is a sign because it can be measured.

What Is a Disease?

A disease is a condition that affects the normal working of the body or mind. It may affect one organ or several organ systems.

Diseases may result from pathogens, poor nutrition, lifestyle habits or environmental factors.

What Are Pathogens?

Pathogens are disease-causing organisms. They may include:

• Bacteria
• Viruses
• Fungi
• Protozoa
• Worms

Diseases caused by pathogens may spread from an infected person to a healthy person.

Communicable Diseases in Health: The Ultimate Treasure Notes

Communicable diseases are caused by pathogens and can spread from one person to another. Their spread depends on the pathogen and mode of transmission.

Modes of Disease Transmission

Pathogens may spread through:

• Air
• Direct contact
• Indirect contact
• Contaminated food
• Contaminated water
• Mosquitoes and other insects
• Contact with infected animals

Insects that transmit pathogens are called vectors.

Diseases Spread Through Air

Air-borne pathogens may spread when an infected person coughs or sneezes.

Covering the nose and mouth, maintaining hygiene and avoiding close contact can reduce transmission.

Diseases Spread Through Contaminated Food and Water

Contaminated water and food may carry disease-causing organisms into the digestive system.

Boiled water, properly cooked food and good sanitation help prevent these diseases.

Diseases Spread Through Insects

Mosquitoes can act as vectors and carry pathogens between people.

Mosquito breeding increases in standing water. Containers, coolers and drains should not be allowed to collect water.

Prevention of Communicable Diseases

Important preventive steps include:

• Washing hands with soap and water
• Covering the mouth while coughing or sneezing
• Wearing a mask in crowded places when needed
• Avoiding shared towels and handkerchiefs
• Drinking clean or boiled water
• Eating properly cooked food
• Keeping surroundings clean
• Preventing mosquito breeding
• Staying home and resting when unwell
• Taking recommended vaccines

Parasites and Worm Infections

Parasites live in or on another living organism and obtain nourishment from it. Some worms live inside the digestive system.

They may spread through contaminated food, water, soil or contact with infected organisms.

Non-Communicable Diseases in Class 8 Chapter 3 Science Notes

Non-communicable diseases do not spread from person to person. They may be linked with lifestyle, diet, nutrition or the environment.

Difference Between Communicable and Non-Communicable Diseases

Lifestyle-Related Diseases

Lifestyle-related diseases may develop due to unhealthy eating habits, lack of exercise or other factors.

Examples include:

• Obesity
• Diabetes
• High blood pressure
• Heart disease

Eating a balanced diet and staying physically active can reduce risk.

Diabetes

Diabetes is becoming common among adults and children. It may develop due to several factors.

These include hormonal imbalance, unhealthy eating habits, lack of activity and being overweight.

Common signs and symptoms may include:

• Frequent urination
• Excessive thirst
• Weight loss
• Tiredness
• Slow healing

Deficiency Diseases

Deficiency diseases develop when the body does not receive enough of a particular nutrient.

Examples include:

• Scurvy
• Anaemia
• Goitre

These diseases are non-communicable because they are not caused by pathogens.

Chronic Diseases

A chronic disease lasts for a long period, often more than three months. It may require continuous treatment and care.

Diabetes, asthma and cancer are examples of diseases that may become chronic.

Kamal Ranadive and Cancer Research

Dr Kamal Ranadive studied links between hormones, viruses and cancer. Her work supported cancer research and prevention.

She also highlighted how tobacco, diet and pollution may increase cancer risk.

Disease Prevention in Class 8 Science Health Notes

Preventive action can reduce the spread of communicable diseases and lower the risk of non-communicable diseases.

Role of Sanitation

Good sanitation includes access to clean toilets, safe water and proper waste disposal. It reduces contact with disease-causing organisms.

A sanitation campaign in Bhadrak, Odisha, increased toilet use and reduced cases of diarrhoea and infection.

Preventing Communicable Diseases

Communicable diseases can be controlled through:

• Clean drinking water
• Safe food
• Handwashing
• Vaccination
• Isolation when required
• Mosquito control
• Clean surroundings
• Proper cough hygiene

Preventing Non-Communicable Diseases

Risk can be reduced through:

• Balanced nutrition
• Regular physical activity
• Proper sleep
• Reduced screen time
• Avoiding tobacco and alcohol
• Managing stress
• Regular health checks
• Early diagnosis

Immunity and Vaccines in Class 8 Science Chapter 3 Notes

The body has a natural system that fights disease-causing organisms. This protection differs among individuals.

What Is Immunity?

Immunity is the natural ability of the body to resist and fight diseases. The immune system identifies and attacks harmful pathogens.

Some people may fall ill more often because their immune response differs.

What Is Acquired Immunity?

Acquired immunity is protection developed after exposure to a pathogen or vaccine. The immune system learns to recognise the pathogen.

On later exposure, the body may produce a faster and stronger response.

How Do Vaccines Work?

Vaccines train the immune system to recognise specific pathogens. They may contain:

• Weakened pathogens
• Dead pathogens
• Inactive pathogen parts
• Harmless components that trigger an immune response

Vaccines prevent disease. They do not cure an infection that has already developed.

Edward Jenner and the Smallpox Vaccine

Edward Jenner observed that milkmaids who had cowpox did not develop smallpox. He proposed that cowpox provided protection.

His work led to the development of the first vaccine. Mass vaccination later helped eradicate smallpox.

Variolation in India

Before modern vaccines, a traditional method called variolation was used in India. Material from smallpox sores was introduced into the skin to produce a mild infection.

People who performed this practice were known as teekedaars.

India’s Role in Vaccine Production

India produces vaccines on a large scale and supplies them to many countries. Indian companies also contributed during the COVID-19 pandemic.

Dr Maharaj Kishan Bhan played an important role in developing the Rotavirus vaccine. It protects children from diarrhoea caused by rotavirus.

Antibiotics in Class 8 Science Chapter 3 Notes

Antibiotics are medicines used against bacterial infections. They kill bacteria or stop their growth.

When Are Antibiotics Used?

Doctors may prescribe antibiotics when an illness is caused by bacteria. These medicines target bacterial structures or processes.

Antibiotics do not work against:

• Viruses
• Protozoa
• Diseases not caused by bacteria

Therefore, antibiotics cannot cure common viral infections such as a cold or flu.

Discovery of Penicillin

Alexander Fleming discovered penicillin in 1928. He noticed that a mould growing on a petri dish stopped nearby bacteria from growing.

The mould released a substance that killed bacteria. This substance became the first widely used antibiotic.

Antibiotic Resistance Class 8 Notes

Antibiotic resistance develops when bacteria survive an antibiotic that previously killed them. These bacteria multiply and may spread.

How Does Antibiotic Resistance Develop?

Resistance may increase when:

• Antibiotics are taken without need
• A doctor’s prescription is ignored
• The full course is not completed
• The wrong dose is taken
• Antibiotics are used unnecessarily in animals

Some bacteria survive treatment and reproduce. They may also transfer resistance to other bacteria.

Why Is Antibiotic Resistance Dangerous?

Resistant infections are harder to treat. They may lead to:

• Longer illness
• More complications
• Longer hospital stays
• Reduced effectiveness of medicines
• Greater risk of death

Correct Use of Antibiotics

Antibiotics should be taken:

• Only when prescribed by a doctor
• In the correct dose
• At the correct time
• For the complete prescribed duration

Unused antibiotics should not be shared with another person.

Traditional Medicine and Disease Management

Ayurveda, Siddha and Unani have been used in India for managing some health problems. They may use herbs, oils, minerals, diet and lifestyle practices.

These systems may support well-being but may not treat every disease or every stage of illness.

Non-communicable diseases may require medicines, lifestyle changes and rehabilitation. Early diagnosis and regular care can reduce complications.

Important Terms in Class 8 Science Chapter 3

Quick Revision of Chapter 3 Science Health: The Ultimate Treasure

• Health includes physical, mental and social well-being.
• Lifestyle and surroundings affect health.
• Symptoms are felt, while signs are observed or measured.
• Communicable diseases are caused by pathogens.
• Non-communicable diseases do not spread between people.
• Mosquitoes and houseflies may act as vectors.
• Hygiene, clean water and sanitation prevent infections.
• Immunity is the body’s ability to fight disease.
• Vaccines provide protection before disease develops.
• Antibiotics work against bacteria, not viruses.
• Incorrect antibiotic use can cause resistance.
• Healthy habits reduce the risk of many diseases.

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