Spider veins worsen by crossfit?

It is difficult to pinpoint the exact cause of your spider veins, as there are many factors that can contribute to the development or worsening of spider veins. Standing or sitting for long periods of time can increase spider veins, but excessive pressure on the veins from intense workouts could contribute, although exercise is generally good for your veins. I suggest you visit a board-certified dermatologist who specializes in sclerotherapy to see if you are a candidate for the procedure.

Many reasons can make you perceive that you are getting more spider veins after exercize but what you are experiencing (most likely) is increased body temperature and more blood pooling in the skin during and for a period after exercize (vasodilation) - therefore not related

In general exercise is good for veins because the muscle contractions increase the venous return and reduce the venous pressure in the legs. However, pounding or jarring may not be beneficial to the veins. Exercises such as running on hard surfaces and squats may put pressure on the venous valves leading to increased vein formation. I have not seen any specific study to prove this but I have seen this occur numerous times over the years. You may want to consider a venous reflux exam to assess the status of your veins for reflux.

Spider veins can appear at any time. They are genetic, brought on by weight changes, and can also occur from excessive workouts or strain. It's hard to blame it totally on Crossfit as it could have just been a time in your life when they were going to develop either way. There are treatments options if you'd like to visit a dermatologist for an assessment for either sclerotherapy (this is my preference) or lasers. "This answer has been solicited without seeing this patient and cannot
be held as true medical advice, but only opinion. Seek in-person
treatment with a trained medical professional for appropriate care."