According to Wikipedia liquorice can cause high blood pressure.

Liquorice
Consumption of liquorice (which can be of potent strength in liquorice candy) can lead to a surge in blood pressure. People with hypertension or history of cardio-vascular disease should avoid liquorice raising their blood pressure to risky levels. Frequently, if liquorice is the cause of the high blood pressure, a low blood level of potassium will also be present.

Liquorice extracts are present in many medicines (for example cough syrups, throat lozenges and peptic ulcer treatments).

first I've heard of that.

I don't eat much liquorice, actually it's rare that I'll eat liquorice so I can't blame high blood pressure on that.

Oh well, I'd better keep reading I suppose.