what syptoms can parasites cause,are they the same as worms,

worms are one type of parasite ie an internal one.  If you are meaning a skin parasites such as fleas, ticks, mites etc, you will have to say which one or which symptom as they all differ.

what do mites produce,do parasites produce bald spots,or how do dogs get small bald spots

Yes parasites can cause bald spots but so can lots of other conditions for instance inbalances of glandular activity, thyroid etc. which can cause serious illhealth, well, as can parasites too, so really a trip to the vet is in order as only a visual examination, blood tests etc can produce an accurate diagnosis.  You can never achieve that on the internet I'm afraid :)

thanks,