An infection is the invasion of the body by a disease-producing organism

How do the uv rays cause damage?   what exactly causes the skin to burn;   can you be more specific about this mechanism?   3. how do photosensitive medications increase a person's sensitivity to sunlight and therefore increase their risk of getting burned?     what kind of medications can increase photo-sensitivity, can you think of some examples?

True or false. mucous membranes secrete mucus that traps pathogens.

How much serem is need to make kids?