In your hair analysis, did they test for heavy metal contamination like mercury? Have you done any liver flushing? I mostly frequent the Iodine supplementation forum and someone over there told me that the typical way a hair test is read it may miss mercury contamination. Have you had metal (amalgam) fillings in your teeth? It seems like a smart group and you might pose some of your questions to them. Of course the recommendation at the top of the list is going to be Iodine and the companion nutrients. If your minerals are low, that for sure is important to get into your diet. I am supplementing with Lugol'sIodine and some natural thyroid hormone, among some other things I'm trying, most recently an essential oil product for parasites from Young Living and Lauricidin, a monolaurin (coconut oil derived product) that is supposed to be effectively anti-bacterial and antifungal without harming the good bugs.
I am not sure what your symptoms would suggest, but I typically hear that skin eruptions happen with things like "liver heat" from a traditional Chinese medicine standpoint (in which case I would probably do some Liver Flushing since some folks say that also helps their allergies), or because other pathways of elimination are clogged - the colon, kidneys, lymph, liver, etc. and so the body tries to detox through the skin. I have had a "bad gut" for years and tried many things. Actually the diet that helped me the most (when I could stay on it) was the Specific Carbohydrate Diet (also called SCC diet), and I still follow sort of a cheater's version of it. Google it. The premise is that certain types of sugars and carbs have a molecular structure which feeds "bad bacteria" in the gut, whereas others (like fruit and honey, apparently) break down quicker and so do not cause a problem. It's geared toward people with colitis and Crohn's but is supposed to help bowel issues in general. I found it best to avoid the sweeter stuff in the beginning, and better to eat the allowed sugars/carbs separately from protein.
I'm at a point where I'm not sure this is a battle I can ever win, but I'm learning how to manage it. Hopefully you'll have success. At only 18, you haven't had the years of damage that some of us have, so that's in your favor.