April 16 (Reuters) - The Dow and the S&P 500 opened higher on Tuesday, with health insurers leading the charge following upbeat results from industry major UnitedHealth, while investors kept tabs on the conflict in the Middle East.

The Dow Jones Industrial Average rose 257.11 points, or 0.68%, at the open to 37,992.22.

The S&P 500 opened higher by 2.77 points, or 0.05%, at 5,064.59, while the Nasdaq Composite dropped 28.64 points, or 0.18%, to 15,856.38 at the opening bell. (Reporting by Shashwat Chauhan in Bengaluru; Editing by Maju Samuel)