CBSE Class 9 Answered

Fever is a condition which indicates an infection in the body. When pathogens infect the body, they release a substance into our blood called pyrogens. Fever is one of the ways by which immune system tries to combat the infection. The body temperature rises above its normal temperature i.e. 37°c or 98.6 degree Fahrenheit.

Cold is caused by different viruses which makes it difficult for our immune system to produce memory cells. Therefore, cold occurs frequently.

(Memory cells: White blood cells which store the information about the past infections caused in the body. In case the body gets infected by the same pathogen, these cells produce specific antibodies against the infection).