Frequent diarrhea in adult

Hi, my husband, 39 years old, Rod, has a weak(?) constitution.  He cannot eat spicy foods or beans, because it affects his bowel movments negatively.  I can eat spicy foods and beans and even our toddler enjoys the spicy foods I eat, with no ill effects.  

For the past few days, Rod has had frequent diarrhea.   We've been married for 5 years, and he has had this problem before.   He jokes that he gets diarrhea from eating fast food burghers, so I tell him not to eat fast food items.

Now, that he has had his umpteenth bout of diarrhea, I'm wondering if he has IBS or some other gastro issue.  I have had occasional diarrhea when I've eaten tainted food, but my bowels are back to normal within a day.  

I don't believe what my husband has is normal.   Can anybody offer any suggestions?  Thank you very much.