New Era Comb A combines ferr phos, kali phos and mag phos. In tissue salt use, ferr phos is commonly linked with the early stage of inflammation, kali phos is often chosen when nerve irritation leaves you sensitive or worn down, and mag phos is the mineral most often associated with cramping and spasmodic pain.
That makes Comb A one of the nerve-oriented blends in the range. It is usually chosen when discomfort is shooting, burning, twitchy or cramp-like rather than simply stiff. The added biotin is a small nutrient addition that supports normal nervous system function, which fits the way this product is traditionally used.
The combination reflects the way mag phos and kali phos are often paired in tissue salt practice for nerve and muscle tension, while ferr phos is included when heat or tenderness are part of the picture. If you are buying for sciatica-style symptoms, that blend is the main thing to look at.