I don't know what causes it, but if you happen to find out, be sure to let me know as well. The only thing I can say is to see a dermatologist, I was presrcribed doxycycline and it worked pretty well, not 100%, but maybe 80%, which is still pretty good.
Also to your question about the soda, it's possible, sugar seems to aggravate the skin, for the past year, I've just about avoided everything with sugar in it. But I think the main thing to keep in mind, is that it's hormonal fluxuation that is the killer. Eating sugar on an empty stomach will cause your insulin levels to sky rocket, where as eating sugar with a meal will do much less. Also eating meals spread out through the day, maybe 6 instead of 3 will keep insulin levels more balanced. Further, drinking tons of water helps, a body wash with salicylic acid (available at any drug store), and a vitamin called MSM have done a lot for me...
The same thing happened to me with back acne.
Only difference, I started getting back acne at 34.
Your Husband's body is probably producing alot of oil and this is whats causing the body acne.
The best product for body acne is Doxycycline.
You got to get this prescribed from a derm.
Doxycycline will control the oil your body is producing and bring down the body acne and stop it from growing.
There's 2 version of doxycycline. One version costs 25 dollars and another version which is called Dorf, costs 162 dollars.
The one thats 162 dollars is the pure form version.
My pharmacist said there basically the same thing.
I get the one that's 25 dollars.
There is no shelf product you can buy that will stop the acne from growing.
Only an anti biotic will stop it.
The Doxycycline is 30 pills. Get the version thats 100 mg.
Take one pill a day.
I would also recommend using Neutrogena Body Clear Body Scrub.
This has 2 percent Salicylic Acid and is very good for body acne.
Its the best scrub i'v used for body acne.
Leave this on your body for like 2 minutes then wash off.
When your body acne goes down you might have redmarks from the body acne.
The best thing for this is an AHA product.
I would recommend the Neostrata body lotion with 10% AHA.
Neostrata invented AHA.
Its great for getting rid of redmarks.
I use after I take a shower. It blends in the skin better.
Just type in Neostrata aha lotion in google.
Alpha Hydrox makes a good AHA body lotion.
It has 10% AHA.
It can be used for the body and face.
They sell it in Eckerd and Riteaid.
Its called Alpha Hydrox enhanced lotion