Since I already know that my food allergies cause palpitations and increased heart rate, I started poking around to see if they could cause hypertension too.

A while back Dianyla posted a chart of histamine pathways in the body. Yup, hypertension is on there.

Up until now it hasn't really been worth it to me to adhere strictly to my allergy diet. It was like a 30% improvement in quality of life for a 200% increase in hassle. But if it'll keep me off BP meds I'll work at it. Maybe your DH should try a challenge diet, especially if he has known allergies of any type.