My husband is expose daily to the sun being a car sales man. His skin
is very light except for his face and neck which is totally over
tanned. His neck up to the  collar line is more tanned than his face
which makes me wander why is this. Even before he became a salesman,
his neck is already super tanned. He won't use any suntan lotion
because he said it is greasy and sticky. What causes this red neck and
how to protect the skin besides sun tan lotion? Hats and umbrella not
allowed except when it rains.

He should use some sun screen lotion.

It's not only unsightly but potentially unhealthy.

I'm also a sufferer.

The only other thing I can think is that you can get dark pigmentation
on the back of the neck with hyperinsulinemic states (as in type II
diabetes) but it's not usually red, it's dark (often described as
looking 'dirty').
Far and away the most likely thing is sunburn.  Check with a larger
department store or online for better sunscreens that are nongreasy
(Neutrogena makes one) and contain avobenzone (so you're getting UVA
and UVB protection).

There are many suntan lotion products that claim to not leave a greasy
sticky residue.  Here is 1:
http://www.americarx.com/index.asp?PageAction=VIEWPROD&ProdID=11862

Search the web or the drug store for these products and I'm sure you
can find something that his old objections won't work for.  Of course
he'll come up with new objections, but you need to be persistent and
let him know that you care and are worried about his health in this
matter.

Turtle neck sweater knit of cotton or some light material.

Does firm have a casual Friday dress code?  

Bond ....     James Bond     

Drives a flashy car.

Thank you all for your comments. I will show your comments to my husband.
I'll find a non greasy lotion and apply the suntan lotion on his neck myself.

This is called poikiloderma