Selina Concise Solutions for ICSE Class 7 Biology Chapter 7 Allergy

Review Questions

Question 1: Define the term “allergy”.
Answer:
Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to something in the environment that usually causes no adverse effects to most people. These diseases include hay fever, dermatities, asthma, food allergies, etc.
An allergy happens when your body's immune system overreacts to a harmless substance as if it were a dangerous invader. This mistake by the immune system leads to symptoms that can range from a simple sneeze to serious breathing difficulties.
Teacher's Tip: Think of an allergy as your body's "False Alarm" system going off for no reason.
Exam Tip: Always include keywords like "hypersensitivity" and "immune system" to score full marks in this definition.

Question 2: Name the inflammatory chemical released by the basophils causing skin reaction and construction of the bronchioles.
Answer:
The histamine causes inflammation, skin rash and constriction of the bronchioles (as in asthma).
Histamine is the main chemical messenger your body produces during an allergic reaction to signal cells to react. It is responsible for the redness, swelling, and itching that we usually associate with allergies.
Teacher's Tip: Just remember: Histamine starts with "H", and it causes "H"ives and "H"ay fever.
Exam Tip: If the question asks for a specific "chemical," make sure "Histamine" is the very first word in your answer.

Question 3: How the allergy causing chemical is naturally removed from the body ?
Answer:
There are no permanent cure for an allergy. Medication for allergies do give relief. Those people prone to allergic reactions should be aware of the allergens that trigger these responses in their bodies and avoid them completely, especially food and medicines. Allergy shots are helpful to those with seasonal allergies like those caused by pollen.
While the body eventually breaks down chemicals like histamine, the best way to handle allergies is to avoid the trigger entirely. For long-term management, doctors use immunotherapy or "allergy shots" to help the body become less sensitive over time.
Teacher's Tip: The best medicine for an allergy is "Avoidance" - if you don't touch it, you won't react!
Exam Tip: Mention that there is "no permanent cure" to show you understand that allergies are chronic conditions.

Question 4: Match the items given under column I with those given under column II.
column I
(i) Dust allergy
(ii) Food allergy
(iii) Seasonal allergy
column II
(a) Nuts
(b) Pollen
(c) Asthma
Answer:
column I - column II
(i) Dust allergy - (c) Asthma
(ii) Food allergy - (a) Nuts
(iii) Seasonal allergy - (b) Pollen
This matching exercise shows how different triggers lead to specific allergic conditions or are found in specific categories. For example, nuts are a very common food trigger, while pollen only appears during certain times of the year.
Teacher's Tip: Use "P" for "P"ollen and "P"eriodic/Seasonal to remember that one easily.
Exam Tip: When matching, draw straight lines or write the corresponding letters clearly next to the Roman numerals.

Question 5: Name any three routes of which allergens normally enter in our body.
Answer:
1. Skin - Substances that come into contact with the skin, such as latex, are also common causes of allergic reactions, known as contact dermatitis or eczema.
2. Mouth - A wide variety of foods can cause allergic reactions, but 90% of allergic responses to foods’are caused by cow’s milk, soy, eggs, wheat, peanuts, tree nuts, fish and shellfish.
3. Nose - Pollen, spores, dust particles and certain chemicals find entry through the nose.
Allergens can enter our system through breathing, eating, or even just touching the surface of our body. Each route of entry typically results in different symptoms, such as sneezing from the nose or rashes from skin contact.
Teacher's Tip: Use the "S-M-N" trick: Skin, Mouth, and Nose are the three gates of your body.
Exam Tip: Provide a specific example (like latex for skin) for each route to make your answer more descriptive.

Question 6: What are allergens ? Name any three allergens.
Answer:
The substances that cause allergies are called allergens.
1. Dust particles
2. Nuts
3. Pollen
An allergen is any substance that is normally harmless but triggers an allergic response in sensitive individuals. Common allergens are often microscopic, such as bits of dust or tiny grains of pollen floating in the air.
Teacher's Tip: Think of "Allergen" as the "Allergy-Generator."
Exam Tip: When naming three allergens, choose distinct ones like a food, a seasonal item, and an indoor item.

Question 7: Name the two tests generally used to diagnose allergy and describe any one of them.
Answer:
1. Prick Test-Skin prick test is also known as “puncture testing” or “prick testing” due to the series of tiny punctures or pricks made into the patients skin. A small plastic or metal device is used to puncture or prick the skin. Sometimes, the allergens are injected intradermally into the patients skin, with a needle and syringe. Small amounts of suspended allergens or their extracts (e.g., pollen grain, insect sting proteins, peanut extracts) are introduced to sites on the skin marked with pen or dye. Common areas for testing include the inside of forearm and the back.
2. Blood Testing - A sample of the patient’s blood is sent to a laboratory for analysis. Multiple allergence can be detected with a single blood sample. The test measures the concentration of specific antibodies in the blood. The quantitative allergy blood result can help determine what a patient is allergic to, help predict and follow the disease development, estimate the risk of a severe reaction, and explain cross-reactivity.
Doctors use these tests to identify exactly which substances are causing your immune system to overreact. While the prick test gives fast results on the skin, the blood test is very accurate for identifying many different triggers at once.
Teacher's Tip: The Prick Test is like a "live experiment" on your skin, while the Blood Test is a "lab report" for your immune system.
Exam Tip: If asked to describe "any one," choose the one you remember the most details for, such as the sites used for the prick test.

Question 8: Which test is mostly favoured for testing allergy, prick test or blood test ? Why ?
Answer:
Blood test is mostly favoured for testing allergy.
Blood Testing - A sample of the patient’s blood is sent to a laboratory for analysis. Multiple allergence can be detected with a single blood sample. The test measures the concentration of specific antibodies in the blood. The quantitative allergy blood result can help determine what a patient is allergic to, help predict and follow the disease development, estimate the risk of a severe reaction, and explain cross-reactivity.
The blood test is preferred because it is safer for patients who might have a very severe reaction to a skin prick. It also allows doctors to check for many allergies simultaneously without causing any skin discomfort or rashes.
Teacher's Tip: Blood tests are "One and Done" - one needle poke can check for dozens of allergies!
Exam Tip: Always explain the "Why" part clearly by mentioning safety and the ability to detect multiple allergens.

Additional Questions

Multiple Choice questions :

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Hay fever and asthma are
(i) Deficiency diseases
(ii) Genetic diseases
(iii) Organic diseases
(iv) Allergy diseases
Answer: (iv) Allergy diseases
Hay fever is an allergic reaction to pollen, and asthma is often triggered by airborne allergens like dust. Both conditions involve an overactive immune response in the respiratory system.
Teacher's Tip: These are "Breathing" allergies, so they belong to the allergy disease group.
Exam Tip: Don't get confused by "Genetic diseases"; while you can inherit the tendency to have allergies, the diseases themselves are classified as allergies.

(b) Cataract is a disease of:
(i) Ears
(ii) Nose
(iii) Eyes
(iv) Throat
Answer: (iii) Eyes
A cataract is the clouding of the lens inside the eye, which leads to a decrease in vision. It is most common in older adults and is not related to allergies.
Teacher's Tip: Eye doctors check for cataracts, so it must be an eye disease.
Exam Tip: Remember that not every disease in this chapter is an allergy; some are included for comparison.

(c) Infectious diseases can be prevented by:
(i) Medicines
(ii) Proper food
(iii) Immunisation
(iv) Exercise
Answer: (iii) Immunisation
Immunisation, or vaccination, helps the body build up a defense against specific germs before you actually get sick. This is different from allergy management, which usually focuses on avoiding triggers.
Teacher's Tip: Immunisation is like giving your body a "wanted poster" for germs so it knows who to fight.
Exam Tip: While healthy food and exercise help, "Immunisation" is the specific medical method for disease prevention.

(d) Which one of the following is a genetic disease ?
(i) Scurvy
(ii) Leukemia
(iii) Goitre
(iv) Haemophilia
Answer: (iv) Haemophilia
Haemophilia is a disorder where the blood does not clot properly because it is missing certain proteins. It is passed down from parents to children through their genes.
Teacher's Tip: Think of Haemophilia as a "Family Heritage" disease because it's in the genes.
Exam Tip: Genetic diseases are present from birth, unlike deficiency diseases like scurvy which happen later due to diet.

(e) Which one of the following is a degenerative disease ?
(i) Thalassemia
(ii) Beri-beri
(iii) Cataract
(iv) Diabetes
Answer: (iii) Cataract
Degenerative diseases are those where organs or tissues wear out or break down over time. Cataracts happen when the proteins in the eye's lens change and clump together as a person ages.
Teacher's Tip: "Degenerate" means to break down or wear out with age.
Exam Tip: Cataract is a classic example used for degenerative diseases in most science textbooks.

(f) Pellagra is one disease caused by the deficiency of:
(i) Vit.B3
(II) Vit.B1
(iii) Vit. C
(iv) Vit. D
Answer: (i) Vit.B3
Pellagra is a deficiency disease that affects the skin, digestion, and the nervous system. It occurs when a person does not get enough Niacin, which is also known as Vitamin B3.
Teacher's Tip: Just match the "3" in B3 with the "P" in Pellagra using a mental link.
Exam Tip: Be careful not to mix up the different B vitamins; B1 is for Beri-beri and B3 is for Pellagra.

(g) Deficiency of Iodine in one’s food can cause :
(i) Beri-beri
(ii) Goitre
(iii) Scurvy
(iv) Pellagra
Answer: (ii) Goitre
Iodine is essential for the thyroid gland to produce hormones; without it, the gland swells up, creating a lump in the neck called a goitre. Using iodized salt is a common way to prevent this condition.
Teacher's Tip: Iodine and Goitre both have a "neck" connection!
Exam Tip: Deficiency diseases are a common topic; memorizing the table of minerals/vitamins and their diseases is a must.

Short Answer Questions:

1. (a) What is a non-communicable disease ?
Answer: The diseases which are caused due to improper functioning of the body organs e.g. diabetes, heart attack. They are not caused by germs and not transmitted from one to another.
Unlike the flu, you cannot "catch" a non-communicable disease by standing next to someone who has it. These are internal health issues caused by genetics, lifestyle, or aging.
Teacher's Tip: "Non-communicable" means "Can't be shared."
Exam Tip: Always provide an example like "heart attack" to complete your explanation.

(b) What is a deficiency disease ?
Answer: These disease are caused by lack of nutrients, vitamins, minerals as a anaemia, goitre.
Our bodies need specific "building blocks" from food to work properly; if we miss one for a long time, we get sick. For instance, lacking iron leads to anaemia because the blood can't carry enough oxygen.
Teacher's Tip: A "Deficiency" is just a fancy word for a "Shortage."
Exam Tip: Mentioning "lack of nutrients" is the key phrase for this answer.

(c) What are communicable diseases ? How can they be avoided ?
Answer: Those disease which spread from one person to another by the entry of microorganisms are known as communicable diseases. The disease-causing germs are called Pathogens. These disease can be avoided by proper vaccination, healthy food and hygenic surroundings.
These diseases are caused by external invaders like bacteria or viruses that travel between people. Staying clean and getting vaccinated helps your body's "army" stay strong enough to fight them off.
Teacher's Tip: "Communicable" means the germ "communicates" or travels between people.
Exam Tip: Use the word "Pathogens" to show you know the scientific term for germs.

(d) Biting nails should be strictly avoided. Give reason.
Answer: Nail biting may cause many disease as the dirt has many bacteria causing diseases. Nails should be cut from time to time to save from diseases.
Your hands touch many surfaces every day, and germs hide in the dark spaces under your fingernails. When you bite them, you are basically swallowing those germs directly into your body.
Teacher's Tip: Your fingernails are like little "germ hotels" - keep them closed!
Exam Tip: Focus on the "bacteria" and "dirt" aspect to explain the biological risk.

(e) Regular exercise and proper rest is a must. Give reason.
Answer: Regular exercise keeps our body strong and immune to many diseases, rest refreshes our body.
Exercise acts like a "workout" for your immune system and heart, making them more efficient at protecting you. Rest is equally important because it's the time when your body repairs itself and recharges its energy.
Teacher's Tip: Think of exercise as "charging the battery" and rest as "saving the work."
Exam Tip: Mention that exercise helps with "immunity" to link it back to the chapter's themes.

(f) Children eating more of fast food tend to suffer from obesity (overweight). Comment.
Answer: Fast food like pizza, burger, patty, oily foods etc. have much carbohydrates and fats. Children eating these become more and more fat and gain weight soon as they do not do much of physical work.
Fast foods are "energy-dense," meaning they have a huge amount of calories in a small package. If you eat that energy but don't burn it off through play or sports, your body stores it as extra fat.
Teacher's Tip: Fast food is "Heavy Fuel" - you need to do a lot of "driving" to use it all up!
Exam Tip: Use terms like "carbohydrates" and "fats" to explain why fast food is problematic.

(g) Define the term “allergy”.
Answer: Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to something in the environment that usually causes no adverse effects to most people. These diseases include hay fever, dermatities, asthma, food allergies, etc.
An allergy is basically your immune system being "too careful" and attacking things that aren't actually dangerous. This creates symptoms like swelling or sneezing that are meant to protect you but end up causing discomfort.
Teacher's Tip: This is a repeat question, which means it is very important to learn!
Exam Tip: Practice spelling "hypersensitivity" correctly as it is a key term.

(h) Name the inflammatory chemical released by the basophils causing skin reaction and construction of the bronchioles.
Answer: The histamine causes inflammation, skin rash and constriction of the bronchioles (as in asthma).
Histamine is the chemical that causes blood vessels to leak, which leads to the swelling and redness seen in rashes. In the lungs, it makes the air tubes (bronchioles) tighten, making it hard to breathe.
Teacher's Tip: Basophils are the cells, and Histamine is the "chemical weapon" they release.
Exam Tip: Mentioning "asthma" as an example of bronchiole constriction helps show the real-world effect.

(i) How the allergy causing chemical is naturally removed from the body ?
Answer: There are no permanent cure for an allergy. Medication for allergies do give relief. Those people prone to allergic reactions should be aware of the allergens that trigger these responses in their bodies and avoid them completely, especially food and medicines. Allergy shots are helpful to those with seasonal allergies like those caused by pollen.
To stop the chemicals from being released, you must stay away from whatever triggers your immune system. If a reaction does happen, medications like antihistamines can block the chemical's effects until it naturally leaves the body.
Teacher's Tip: Removal isn't the goal; "Prevention" and "Blocking" are the keys to allergy management.
Exam Tip: Differentiate between "medication" for relief and "avoidance" for long-term health.

2. Name the following:
1. A viral disease caused due to unhealthy sexual contact AIDS.
2. A bacterial disease caused due to contaminated water Cholera.
3. A disease caused due to Plasmodium Malaria.
4. A disease caused due to the bite of female Culex mosquito Elephantiasis.
5. A viral disease caused by the bite of a dog Rabies/ Hydrophobia.
Answer: (As listed above)
These diseases are categorized by their causes and how they are spread, which is why we call them communicable. For example, some are spread by "vectors" like mosquitoes, while others come from contaminated food or water.
Teacher's Tip: Link the "Vector" (dog, mosquito) to the "Disease" in your memory bank.
Exam Tip: Be specific with mosquito names; Anopheles causes Malaria, but Culex causes Elephantiasis.

3. Write short (1-2 sentences) notes on the following:
Disease, immunisation, allergy, AIDS.
Answer:
1. Disease: Disease is a departure from normal health due to structural or functional disorder of the body. Disease may be due to deficiency of nutrients or malfimctioning of organs or genetic disorders, improper metabolic activity, or allergies, or cancer and mental illness as diabetes, haemophilia, leukemia, schizophrenia.
2. Immunisation : It means, we make the body immune to certain diseases by introducing respective weakened germs into the body. Thus we develop resistance to the concerned disease this process is called immunisation. The germs or the material introduced into the body to make it resistant to the concerned disease is called vaccine. This produces antibodies in the body of the person and the person can be saved by these antibodies. The vaccine can be given by the injection or orally as polio drops, tap vaccine for typhoid, BCG vaccine for tuberculosis.
3. Allergy: Allergy is an unpredictable reaction to a particular substance. This type of substance is called allergen. Different people are allergic to different substances. A few common allergens are dust, spores, pollen, certain clothes, particular cosmetics, etc. The common areas of the body parts which are affected by allergies are skin, respiratory and digestive tracts. Asthma, eczema, diarrhoea, vomiting, nausea, etc. are some of the common allergic reactions.
4. AID’S: (Acquired Immune Deficiency Syndrome): It is a viral disease caused by the virus called HIV ( Human immuno deficiency virus) This virus makes the defence mechanism of the human body very weak. The immune system in the body as W.B.C. becomes weak. Thus the person catches the infectious diseases very easily. This disease spreads through sexual contact as one of the partner may be carrier of the disease. It may spread through the blood transfusion and infected syringes, blades of the barbers, it may infect the developing baby through the blood by the mother. It is very deadly disease.
These notes summarize the different ways our health can be compromised, from external viruses like HIV to internal overreactions like allergies. Understanding terms like "immunisation" shows how modern science helps us fight off many of these threats.
Teacher's Tip: Use "A-I-D-S" to remember it's "Acquired" (you get it from outside) and "Deficiency" (your body lacks defense).
Exam Tip: For short notes, always include the full name of the condition (like HIV for AIDS) to show extra knowledge.

4. Find the odd one out:
(a) Typhoid, cholera, jaundice, tuberculosis, tetanus.
Answer: Jaundice is odd one
Jaundice is a symptom or condition of the liver, whereas the others are specific infectious diseases caused by bacteria. While you can "catch" the others, jaundice is usually an internal organ issue.
Teacher's Tip: Look for the "Germ" diseases versus the "Organ" issues.
Exam Tip: Always provide the reasoning for your choice if space allows.

(b) Cold, AIDS, plague, malaria, measles.
Answer: Malaria is odd one.
The others (Cold, AIDS, Measles) are primarily viral diseases, or spread directly between people in the case of Plague. Malaria is unique here because it is caused by a protozoan and requires a mosquito vector to spread.
Teacher's Tip: Think about "How it's caught" - mosquitoes are the key difference for Malaria.
Exam Tip: If you choose an odd one, make sure you can explain why the other four are similar.

(c) Scurvy, rickets, haemophilia, pellagra, night blindness.
Answer: Haemophilia is odd one.
The other four are all deficiency diseases caused by a lack of vitamins in the diet. Haemophilia is a genetic disease that you are born with, regardless of what you eat.
Teacher's Tip: It's "Diet vs. DNA."
Exam Tip: Memorize the vitamin names for the others: Scurvy (C), Rickets (D), Pellagra (B3), Night Blindness (A).

(d) Proteins, carbohydrates, fats, minerals, cancer.
Answer: Cancer is odd one.
The first four are essential nutrients that our body needs to stay healthy and function. Cancer is a serious disease where cells grow uncontrollably; it is not a part of nutrition.
Teacher's Tip: Four are "Good stuff from food," one is "A serious illness."
Exam Tip: This is a very easy one, but be careful to read all words so you don't rush through it.

Long Answer Questions:

Question 1: What is vaccination ? Mention the four ways in which vaccine’s are prepared, giving the name of one disease for which each type of vaccine is used.
Answer:
For developing resistance in the body we introduce germs or germ substances in the body to develop resistance in the body against a particular disease. The material introduced into the body is called vaccine, this practice is called prophylaxis. The germ or the germ substance is put into the body orally as polio drops or it is introduced by injection as TAB vaccine. Vaccine or vaccination was attached with small pox, but it is now used in a general sense.
Preparation:
1. Killed germs are introduced into the body These act as vaccine for TAB, vaccine for typhoid, Salk’s vaccine for poliomyelitis. Rabies vaccine for dog bite.
2. Living weakened germs: The living germs are treated in such a way that they become very weak and as such, they cannot cause the disease. They can induce antibody formation such as the vaccine for measles and the freezed dried BCG vaccine for tuberculosis.
3. Living fully virulent germs: These virulent germs in small doses are introduced into the body as vaccine and these ArunDeep’s M-S-Biology-7 109 produce antibodies in the body and these do not allow the germs of particular type to cause that disease. In this vaccination the person is inoculated with cowpox virus. It is very similar to small pox virus.
4. Toxoids : Toxoids are prepared from the extracts of toxins secreted by bacteria. These toxins are poisons and these are made harmless by adding formalin into them. They retain their capacity and as a result when introduced into the body they produce antibodies into the body and do not allow the germs to grow in the body as vaccines for diphtheria and tetanus.
Vaccination works by "training" your immune system to recognize a threat without actually making you sick. By using these four methods, scientists can create safe ways to protect us from some of the world's most dangerous diseases.
Teacher's Tip: Use the keywords "Killed," "Weakened," "Virulent," and "Toxoids" to remember the four categories.
Exam Tip: For long answers, make sure to give at least one example of a disease for each preparation method to get full points.

Question 2: Name the tests generally used to diagnose allergy and describe any one of them.
Answer:
1. Prick Test-Skin prick test is also known as “puncture testing” or “prick testing” due to the series of tiny punctures or pricks made into the patients skin. A small plastic or metal device is used to puncture or prick the skin. Sometimes, the allergens are injected intradermally into the patients skin, with a needle and syringe. Small amounts of suspended allergens or their extracts (e.g., pollen grain, insect sting proteins, peanut extracts) are introduced to sites on the skin marked with pen or dye. Common areas for testing include the inside of forearm and the back.
2. Blood Testing - A sample of the patient’s blood is sent to a laboratory for analysis. Multiple allergence can be detected with a single blood sample. The test measures the concentration of specific antibodies in the blood. The quantitative allergy blood result can help determine what a patient is allergic to, help predict and follow the disease development, estimate the risk of a severe reaction, and explain cross-reactivity.
Allergy tests are vital because knowing exactly what triggers a reaction is the first step toward avoiding it. Whether using the skin's direct reaction or a lab analysis of blood, both tests help doctors create a safety plan for the patient.
Teacher's Tip: Think of these tests as "Allergy Detectives" looking for the culprit!
Exam Tip: When describing the prick test, mention the specific areas of the body (forearm and back) as this is a common detail required by examiners.