Light and loose cotton and pure linen. The person who might be having high blood pressure, will absolutely know how to prevent it.
You will need something breathable, só you do not get hot > uncomfortable > higher blood pressure. Also make sure you also avoid super Tight clothes like super tight socks, as they also cut your blood circulation and can cause bad effects in your body - and lots of discomfort.
Also bet on natural breathable material such as cotton and if you sweat a lot avoid wearing a lot of clothes that will keep you too warm. This will help you remain cool and só will help you control blood pressure.
I had no idea that clothing could affect blood pressure until I read this question but it would seem that if your back is not supported it can raise your diastolic blood pressure by 6mmHg so the type of clothes you wear can have an impact. Tight clothes like belts or elastic compress blood vessels so it's best to avoid these and wear looser clothes.
Blood pressure should also be taken on a bare arm and never over clothes as it will not give a correct reading. Studies have shown that even a shirt rolled up to the elbow can give an inaccurate reading so it is best to wear a sleeveless top.
There is no specific type of clothing material that is better for a person with high blood pressure. However, it is generally recommended that people with high blood pressure wear loose-fitting, comfortable clothing made from breathable fabrics, such as cotton or linen. This can help to reduce the risk of overheating and sweating, which can contribute to fluctuations in blood pressure. Additionally, it is important to avoid tight-fitting clothing and restrictive garments, such as tight belts or waistbands, which can put pressure on the abdomen and affect blood flow.