A student on a school trip started sneezing and wheezing soon after reaching the hill station for no explained reasons. But, on return to the plains, the symptoms disappeared. What is such a response called?

This response (sneezing and wheezing for no explained reasons) is called allergy. The immune response produces such an exaggerated response against a substance called an allergen. The body produces IgE type of antibody against allergens as a response. An example of allergens includes pollen grains, dust, etc.