@FFLinOhio try washing hair less. Also vitamins such as B may help.
@QuasiQuadrant may have herbal recommendations. I agree with
@Ford and
@lsg Diet plays a role and clay based shampoo could be helpful.
I would get your husband going directly to a reputable naturopath in your area. That is happening due to internal imbalance. Your husband's body is overloaded with something which his body is no longer able to properly process itself. Topical products are absolutely not the answer in your husband's case.
Please, don't balk at what naturopaths, or other natural health care practitioners charge. 'Doctors', 'specialists' & 'surgeons' charge even more money & nobody questions this. When more insurance companies fully cover 'alternative' health practitioners, this will become less of an issue. Naturopaths, and others related, need to pay their mortgages, clothe & feed their kids too.
In the meantime, have your husband try taking milk thistle extract. Tinctures can be found - add 1 dropperfull to a small glass of warm water & drink all in one shot. 3 times a day. Or you can buy capsules - not nearly as effective in my personal experience. He may begin experiencing other issues coming out on the skin when beginning to take milk thistle, such as: occasional acne breakouts, dry / flakey skin, itching. This is normal, a result of the liver releasing 'stuff'. I'll leave it at that. After a week or a couple of weeks, he will begin noticing the opposite happening. Skin will be clearer, smoother.
There is also a website called ABC Homeopathy, which has a 'remedy calculator', so to speak. Your husband can input his symptoms, and the most closely matched remedies for him will be suggested. They can be bought directly through that website as well.
Seeing an actual homeopath would also be a good idea, but choose just as carefully as you would with any other type of doctor. There is no one-size-fits-all.
https://abchomeopathy.com/go.php
Do NOT buy your supplements, herbal remedies or health-balancing products in pharmacies, for the love of baby jeebus....go to a good health food store. Whole Foods is NOT a health food store FYI. Hit up a local, independently owned health food store.
FYI I am not a 'doctor' & don't pretend to be one. I am a lifelong user / maker / harvester of traditional plant medicines. Use your common sense, don't rely on anyone else to do your due diligence. Take responsibility for your own health - your husband likewise.
Good luck
Highly functional however, which is what matters, ultimately. Bugger all of the parallax monstrosities & Wordpress abominations out there!
Thank you as well 
