Saline nasal spray is generally safe for people with thyroid conditions and high blood pressure. It works by moisturizing the nasal passages and helping clear mucus without affecting blood pressure or thyroid function. However, it's always a good idea to check with your healthcare provider before starting any new treatment, especially if you have chronic health issues or are on multiple medications. If you experience any unusual symptoms after using the spray, such as increased nasal irritation or allergic reactions, stop using it and consult your doctor.