Allegy Class 7 Biology Living Science

Selina Concise ICSE Solutions for Class 7 Biology Chapter 7 Allergy

Match the following answers

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.

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).

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.

4. Match the items given under column I with those given under column II.

column I                                         column II

Answer:
              column I                                         column II

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.

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

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.

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.