If my son tested allergic to yogurt, does that mean yogurt made from cow milk or all yogurt including coconut?

Ask the medical folks who give the tests. In general, meaning don't make a specific assumption for your son, people who have trouble with dairy products do just fine with soy based.

You need to go back to the immunologist or allergist that performed the test (was it skin or blood?) and ask them exactly what was tested. A regular allergy assay doesn't normally include yogurt. They may have tested for casein or other proteins found in dairy and were not clear when they communicated the results to you. It is always best to get your results in writing and keep them in a safe place.

it depends on what they tested. if they tested milk yoghurt then he's allergic to that...not soy and coconut yoghurt (which is not yoghurt anyway) are you sure he's "allergic" not "intolerant" as in "lactose intolerance"?

we eat lot of unnatural food ,chemically treated food, animal protein, wrong food combination ,stress cause blood impure its over load its eliminating through sweat, scales of the skin, and mucus ,that is problem,we suppress the toxic in to body again ,it will select a already weakened organ , which organ is affect they show symptom, so we give some name its called disease. Now you got stomach, not nose or lung, your over burden of stomach case this allergy ,do one thing ,One full day you do not eat anything you feel better. follow naturopathy