Could running 1 or 2 days after sclerotherapy cause problems?

The most prudent option would be to follow the advice of your surgeon. Sclerotherapy does require some period of convalescence.Raffy Karamanoukian MD FACS

I recommend that my patients walk regularly for a couple weeks following sclerotherapy to ensure best results, so running should be fine, too. Just be sure to wear your compression stockings as instructed.

I give no limitations to my patients after sclerotherapy. I give the following instructions, among others:  walk immediately upon going home, and do whatever you desire the same or next day. Must wear stockings for 3 months to cover the areas injected (thigh if there was sclerotherapy done in the thigh; knee length if sclerotherapy is limited to the areas below the knee). Avoid exposing the legs to sun for 3 months and use topical creams VenoQuin and VenoLucent.

I encourage patients to get back to their routine as soon as possible after sclerotherapy. We encourage them to walk after the treatment so why not exercise? Running causes the calf muscles to contract to increase the venous return and decrease the venous back pressure which is exactly what compression hose does. The only restrictions I place post sclerotherapy are no hot tubs or hot baths for 48 hours to prevent dilation of the small injected vessels and avoiding sun exposure to the treated areas until they heal-about 10 days.