How does illness affect BP?

Is there any general rule concerning how acute infectious diseases like viruses affect BP? In particular, does having a cold or flu tend to raise or lower BP? If so, in which direction, and by how much? I'm trying to see if I need to make any allowances for my routine BP measurements when I'm sick with a cold (like today) or flu. My diastolic pressure has risen during these past few days of a cold and I don't know if that is related to the cold or not.

I am taking antihistamine but not continuously. How long do the BP effects of chlorpheniramine normally last, and what do they usually look like? What about acetaminophen or codeine (which I have taken intermittently for headaches, migraine, and cough associated with the cold)?

It is not uncommon for blood pressure to rise during a viral infection. The extent will vary from one individual to the next.