Ok, think about it. Does your skin prevent germs from getting inside you?
Does your skin prevent water from leaving the body too quickly? Does your skin protect your insides from getting damaged when you fall? Do you put food on your skin to absorb nutrients, or do you put food in your mouth like a normal person?
These people may end up eating something else or end up having a diet. They will have to find a new way to cope and get around in life than eating that kind of food that they wont have so they have to find other sources of food to stay alive and well
If CO2 was in very small amounts then it would be the limiting factor of photosynthesis, this means the process will take place at a much slower rate because it is lacking one of the raw materials it needs for the process to occur. To find the optimum light intensity you really need all other factors to be at optimum levels or in abundance.
Herpes would be one of them