For systemic healing, taking herbs internally is critical to get to the root of the issue. For psoriasis, a few classes of herbs are appropriate here:
Liver/digestive support: Some of the aforementioned antigens (=antibody generators) that trigger or exacerbate psoriasis may be circulating due to inadequate digestion and detoxification. Therefore, liver and digestive herbs can be useful to help clear unwanted toxins: burdock root (Arctium lappa), yellow dock (Rumex crispus), Oregon grape root (Mahonia aquifolium).
Anti-inflammatory/healing: Some of the herbs listed for topical use may also provide some benefit internally as well. To these I would add: turmeric (Curcuma longa) and gotu kola (Centella asiatica).
Topically, herbs to soothe eczema will be similar to those mentioned for psoriasis. Internally, however, there are some key differences in appropriate herbs. Alteratives and anti-inflammatory herbs remain relevant, and to these I would add anti-histamines to alleviate some of the physical discomfort. (think stinging nettle (Urtica dioica) and Baical skullcap (Scutellaria baicalensis). Lymphatics are also important here because they move the metabolic ‘garbage’ left over from detoxification processes out of the body to clear the offending substance and reduce the allergic response.
Lymphatics: poke root (Phytolacca americana)*, calendula (Calendula officinalis), red root (Ceanothus americana)
*poke root is a ‘low dose’, potentially toxic herb. Use sparingly, preferably under the care of a trained professional.