The causes of high blood pressure and face fever are as follows: 1. When blood pressure is high, the peripheral blood volume pressure increases, and capillary filling of the face occurs when the volume increases, causing fever and heat; 2. When hypertensive patients take calcium ion antagonists, such as nifedipine, nifedipine extended-release tablets, amlodipine besylate tablets and other drugs, the side effect of face fever will occur, and this situation will disappear after 2-3 days. If you have been taking diphenhydramine for a long time and your face gets hot, feverish, flushed and sweaty for a short time after taking the drug, it means that you are not suitable for applying diphenhydramine and should switch to other blood pressure lowering drugs for treatment. If the heat and redness of the face is caused purely by high blood pressure, you can use antihypertensive drugs, and the symptoms may be significantly relieved after the blood pressure is lowered.