Welcome to the forum Sandy !
There are two sorts of UV (urticarial vasculitis) depending on the role of a protein called complement which is an essential element of the immune system. Some people with UV have low complement levels so this sort is known as hypocomplementemic UV, HUV for short. Other people have normal complement levels known as normo complementemic. These people are less likely to have systemic symptoms compared with the HUV folk who often have lupus or lupus like symptoms and may even have vascular organ involvement and other systemic complications.
A lupus work up and full health check is definitely in order. Treatment is much the same as for SLE without HUV or UV, using Plaquenil and then other disease modifying drugs as needed. If you read through the related threads you will see what therapies people are trying and also if I remember rightly, various dietary and complementary strategies that might help with management. This is a highly individual thing, as with lupus.
With autoimmune diseases "boosting" the immune system is not advisable because, if it could be done, the harmful autoimmune disease activity would be boosted too. Our immune systems are not deficient or weak, they are malfunctioning so it would be like putting a higher octane fuel into a motor engine that wasn't firing properly.
In fact there are very few substances that are known to improve immune function. If there were, immunodeficient diseases and HIV/AIDS would be helped.
Of course sometimes there are real vitamin or mineral deficiencies such as anemia, or the risk of deficiencies from using some medicines, so supplements are taken to correct or avoid the problems
Here is a very good thorough article on UV. You might have to register (free) to view Medscape/emedicine but there are other good articles on the topic.
Please let us know how you get on and best of luck