Question

many times you cannot eat hot food due to inflammation/ulceration in mouth explain

Answer 1

Ulcers are actually outer skin layer which gets swelled and have a little amount of pus. The area of skin swelled with pus when bursts exposes the inner layer which has sensory cells. This exposure of sensory cells with food particles causes pain.
The pain receptors (sensory cells) send message to the brain which in turn send another message of pain which causes inflammation.
Hope you get it.

Answer 2

Mouth ulcer is usually due to intake of hot food or more acidic saliva. They may be white and yellowish in colour.

EXPLANATION:

The spicy, hot and salty food items causes very much pain. It causes the burning sensation and also difficult in speaking. Certain condition like iron deficiency, vitamin B12, Crohn's disease or even certain genetic factor may trigger the ulcer condition. For treatment, a solution is prescribed by dentist and hence to reduce the swelling and lesion pain. This may appear where ever in mouth. It has to be treated on time for good relief.