Sclerotherapy: is it true that after treatment of spider veins that the patient should not go in direct sunlight or exercise for 3 weeks afterwards?

Maybe: While you do want to limit exposure after the procedure three weeks is a long time. one week is what I shoot for in terms of exposure. exercise should be limited for about 72 hours. unlikely to have any bad effect after sclerotherapy.

Sclerotherapy: The exercise limitation of 3 weeks is excessive. The first few days after treatment are the most critical since the veins could potentially reopen during the initial fibrosis phase . . . you should be fine to exercise after a few days to a week. In terms of sun exposure, I agree that is is good to avoid excess exposure until bruising & discoloration is gone which can take a few weeks. High SPF.

3 weeks would be: long time. Phlebologists vary, but typically these restrictions go from a few days up to a week or so. There are actually no clinical studies to support any particular time frame. Recommendations are the individual physician's opinion based on what is understood about how sclerotherapy works.