Unfortunately, staining from sclerotherapy is not uncommon. Several things may be done to minimize the occurrence. First, it is important to be mindful of wearing compression stockings after treatment. Ideally, these are worn for 1 week post sclerotherapy. The next thing is to be aware that lower concentration of sclerotherapy and lower volume are associated with better cosmetic results in the long run. So, I am quite okay with leftover medication (it doesn't serve my patient's interest that I empty out all the syringes). It is better to work up to the effective concentration then start high with the hope that one treatment will suffice. In the event, results are less than expected, we can always increase the concentration the following session. In our experience, this has led to much less incidence of hemosiderin staining, though not entirely avoided. Finally, it is important that you visit a vein specialist who is able to search for venous insufficency and possibly explain spider and varicose veins before jumping to cosmetic sessions. If there is underlying venous insuffiency, then treating the source first (larger to then smaller veins) is definitely associated with less incidence of staining. Hope that helps!