My wife has severe neck pain. What advice would you give? Is the application of heat or cold of any help?

The best treatment for neck pain will really depend on what is causing the issue in the first place. For example, if it is down to injury then I would advise seeing your doctor or a physiotherapist who can do a physical examination of the area and offer the most appropriate course of action. However, if the problem is more to do with the likes of posture, gentle movement and stretches are ideal. There are of course several other things that may lead to neck pain besides these.

Again, whether or not head or ice will help will really depend on what the problem is. In general, though, cold helps inflammation, redness, bruising and swelling, whilst heat is good for soothing the muscles, promoting relaxation and reducing pain. You can read more in my blog here.

For general aches and pains, I also tend to suggest Arnica Gel which can aid pain, stiffness and inflammation.
If you would like further advice, I have a blog on neck pain treatments you could have a look at.