Dear Getting There
Raisins will not increase your blood pressure. The people who are telling you to eat raisins are confusing low bp with anaemia caused by an iron deficiency. Raisins are a relatively good source of iron and patients with anaemia are advised to eat some raisins every day to correct their iron deficiency (together with other good sources of iron like red meat and liver). The only change that one can make to the diet to try and increase bp is to add slightly more table salt to foods. It is, however, important that you don't overdo you salt intake as excess intakes can cause kidney problems. You need to discuss this low bp problem with a medical dr because there are medications like Effortil that can help for this condition.
Best regards
DietDoc