Nettle's good for about a zillion reasons; it's high in silica, which is great for hair and nails, and it's particularly supportive of the skin (which is the largest organ of the body, and often the least attended to, in terms of internal support).
Echinacea should not be used by folks who have allergies. The allergic response involves a part of the immune system that is over stimulated; Echinacea stimulates the entire immune system, including the parts that are already over stimulated. For folks who have any sort of immune imbalance, there are several herbs that help balance the immune system (rather than stimulate it) so that it functions at its best:
Astragalus root (astragalus membranaceus), aka Milk Vetch or Chinese (Pin Yin) Huang Qi, is something that can be used in tea or added to soup, stew, and even rice and quinoa. You do have to remove the root before serving when you cook with it because the root is very woody, so best to purchase astragalus in its sliced form (the slices look a bit like tongue depressors). Too, when buying astragalus, the larger the root, the better the potency. It's become so popular that the plant is sometimes harvested too young, and the roots are small. That's not the best, and I think the small amount you'd save buying the younger roots is not worth the lessened potency. A pound of astragalus root should be sufficient for cooking throughout the colder, darker months of the year and really isn't expensive; my best source for this is a local Chinese herb shop, but it can be found online.
Codonopsis root (radix codonopsis), Chinese (Pin Yin) Dang Shen, is often called "poor man's ginseng" because of its ginseng-like properties. I actually think it's a better choice than ginseng, as codonopsis doesn't present the danger of over-stimulation (and increased blood pressure), and is much gentler on the system. Great for balancing the immune system, codonopsis root is another one that can be incorporated into the diet. The root is kind of ugly to look at, but has a lovely, subtle nutty flavor. Bought as dried root, it can easily be re-hydrated and used in soup, stew, rice, quinoa, and even stir fry (among other things). It's also a nice addition to any tea blend.
If you have any questions, please feel free to PM me.